Four active protesters who spoke to CNN for this story requested anonymity because they feared being targeted for their comments. Calvin asked we only use his first name. "Jim," "Bobo" and "Leslie" requested pseudonyms.

The 16-year-old didn't want to abandon the injured man next to him. He applied gauze to stop the man's eye from gushing with blood, but he still was having trouble walking. Jim tried to carry him, but only made it a few feet.

Clouds of tear gas were closing in. Rubber bullets had been flying overhead. The teenager's hours of first aid work on the front line had taken their toll. Physically he couldn't carry the wounded man any more.

All he could do was cry.

Police clash with protesters during a demonstration outside the government headquarters in Hong Kong on June 12.

It was June 12 . Jim had never previously been to a protest. Hours earlier, when he volunteered to help treat the injured, he had no idea that he'd be in the thick of what turned out to be a dangerous encounter with Hong Kong police.

Tens of thousands of protesters took to the streets that day to oppose a controversial bill that would have legalized extradition from Hong Kong to mainland China. The bill was inspired by the city's inability to return the suspect of a grisly murder to Taiwan, but many Hong Kong citizens feared it would be abused by Beijing for political persecution

Protesters move barricades to block a street during the June 12 protest.

Prior to June 12, Jim said he wasn't political. He was a high school student who liked to play the violin. The son of two medical professionals, he had aspirations to one day be a doctor. A demonstration, he thought, would be a good opportunity to put some first-aid training to use.

The rally was given permission by authorities. But by mid-afternoon a number of protesters decided to storm the entrance of the city's legislature despite the heavy police presence.

Police declared the protest a riot and used tear gas and rubber bullets to disperse the crowd. Jim spent about three hours treating the wounded and said what he saw changed him.

He thought the Hong Kong police had used disproportionate and "unreasonable force."

Jim could barely sleep that night and when he did, he had nightmares. He had an exam the next day but said his brain "was totally empty." He sat down at his desk, rested his head on the table and slept.

Protesters run after police fired tear gas outside government headquarters on June 12.

Thousands of young people like Jim have spent the summer on the front lines of Hong Kong's longest sustained protests since the city returned to China in 1997. Their movement started in opposition to the bill but quickly snowballed into a grassroots, decentralized crusade for universal suffrage and independent inquiries into alleged police misconduct.

They want to be able to able to choose their own leader, who is currently appointed by a Beijing-dominated panel.

The scenes have grown increasingly violent throughout the summer. The streets of one of the safest cities in the world now regularly become battlegrounds with police firing rubber bullets and tear gas to disperse illegal demonstrations.

Hong Kong protesters' 5 demands Fully withdraw the extradition bill Set up an independent inquiry to probe police brutality Withdraw the characterization of protests as "riots" Release those arrested at protests Implement universal suffrage in Hong Kong

Protesters say they have become numb to the chaos. Many have become increasingly prone to violence. Those who spoke to CNN about their experiences did so on the condition of anonymity, fearing that they'd be targeted by police or pro-government mobs.

Jim said for him, June 12 was the turning point.

He decided it wasn't enough just to volunteer first aid. It was time to get in on the action, even though he had never been involved in politics or been in a fight. He thought he needed to take a stand against what the police had done.

A police water cannon drives toward protesters on August 25.

July 1

On July 1, at 3 a.m. Jim snuck out of his parents' flat to meet the friends he'd be protesting with. He was "excited and a little bit nervous."

"I was thinking that this time I will be with the guys who are standing on the front lines," Jim said. He wasn't just going to give first aid on the sidelines this time.

The day would end with part of the government's headquarters in ruin and tear gas in the streets, scenes previously considered unthinkable in Hong Kong.

Jim had become part of a "team" of about 20 protesters. Small cells have become commonplace in the leaderless protest movement and replaced traditional top-down organization. People join groups that decide what to do based on online chatter on Telegram, an encrypted messaging app, and an online forum called LIHKG that works like Reddit.

This makes it harder for authorities to track protesters and jail their leaders, a strategy often referred to here as "cutting off the head of the snake."

Jim joined his cell after meeting a member of the team, who according to Jim, seemed brave, eloquent and persuasive. They all met up early in the morning on July 1, the anniversary of when Hong Kong was handed from Britain to China in 1997 under a "one country, two systems" framework that allowed the city more freedoms and its own legal system. That arrangement is due to expire in 2047, when Hong Kong will come under Beijing's direct rule.

Photos: Hong Kong unrest A riot policeman sprays pepper spray at a man as they disperse a crowd during a demonstration against "parallel traders" who buy goods in Hong Kong to resell in mainland China on Sunday, January 5. Hide Caption 1 of 160 Photos: Hong Kong unrest Pro-democracy supporters hold placards as they take part in a New Year's Day rally on Wednesday, January 1 in Hong Kong. Hide Caption 2 of 160 Photos: Hong Kong unrest Pro-democracy supporters wave flags during a countdown party in Tsim Sha Tsui district on New Year's Eve. Hide Caption 3 of 160 Photos: Hong Kong unrest Police arrive to conduct a clearance operation in the Kowloon district of Hong Kong on December 31. Hide Caption 4 of 160 Photos: Hong Kong unrest Protesters take photos of a 'Free HK' light display at a gathering in the Central district of Hong Kong on December 30. Hide Caption 5 of 160 Photos: Hong Kong unrest A man is detained by riot police during a demonstration in a shopping mall at Sheung Shui district on December 28. Hide Caption 6 of 160 Photos: Hong Kong unrest A protester reacts after police fire tear gas to disperse bystanders in the Jordan district of Hong Kong, early on December 25. Hide Caption 7 of 160 Photos: Hong Kong unrest People celebrating the holidays react to tear gas as police confront protesters on Christmas Eve. Hide Caption 8 of 160 Photos: Hong Kong unrest Protesters march in Hong Kong. Hide Caption 9 of 160 Photos: Hong Kong unrest Protesters stage a rally outside the US Consulate in Hong Kong on Sunday, December 1. Hundreds gathered Sunday afternoon outside the US Consulate for another pro-US rally to show support for President Trump after he signed the Hong Kong Human Rights and Democracy Act into law. Hide Caption 10 of 160 Photos: Hong Kong unrest People take part in a march from Tsim Sha Tsui to Hung Hom in Hong Kong on December 1. Hide Caption 11 of 160 Photos: Hong Kong unrest Pro-democracy candidate Jimmy Sham, right, celebrates with a supporter after winning his election in the Sha Tin district, early November 25. "Today's result represents (my constituency's) support to protesters. The government should immediately establish the Five Demands and respond to the public's voices," Sham posted on Facebook, referencing a long-standing protest slogan. Hide Caption 12 of 160 Photos: Hong Kong unrest Pro-democracy candidate James Yu hugs his girlfriend after winning his seat in district council elections, early November 25. Hide Caption 13 of 160 Photos: Hong Kong unrest People line up to vote outside of a polling place in Hong Kong, November 24. More than 2.9 million people turned out to vote in Sunday's elections, which have been framed as a de facto referendum on the almost six months of ongoing protests. Hide Caption 14 of 160 Photos: Hong Kong unrest Hong Kong Chief Executive Carrie Lam casts her ballot for the district council elections at a polling place, November 24. In a statement Monday, Lam said her government "respects the election results." Hide Caption 15 of 160 Photos: Hong Kong unrest A group of protesters leave the Hong Kong Polytechnic University holding hands before surrendering to police in the Hung Hom district on November 22. Hide Caption 16 of 160 Photos: Hong Kong unrest Protesters use clothes and helmets to form "SOS" at Hong Kong Polytechnic University on November 21. Hide Caption 17 of 160 Photos: Hong Kong unrest Protesters raise their hands to represent the five demands of pro-democracy demonstrators during a rally in support of the Hong Kong Human Rights and Democracy Act in the U.S., at the IFC Mall in Hong Kong, on November 21. Hide Caption 18 of 160 Photos: Hong Kong unrest Tables and chairs piled up to create a barrier are left behind by protesters who barricaded themselves inside the Hong Kong Polytechnic University. Hide Caption 19 of 160 Photos: Hong Kong unrest A Fire Services Department rescue diver prepares to enter the sewage system on November 20 to search for protesters who escaped from the Hong Kong Polytechnic University. Hide Caption 20 of 160 Photos: Hong Kong unrest Police detain a group of people after they tried to flee the Hong Kong Polytechnic University campus on November 19. Last week, thousands of student protesters streamed into the university and occupied the campus as the city's violent political unrest reached fever pitch. Hide Caption 21 of 160 Photos: Hong Kong unrest A protester uses a flashlight while crawling through a sewer tunnel to see how wide it is as he and others try to find an escape route from the Hong Kong Polytechnic University on November 19. Hide Caption 22 of 160 Photos: Hong Kong unrest A protester walks through a gymnasium at Hong Kong Polytechnic University on November 19. Hide Caption 23 of 160 Photos: Hong Kong unrest Protesters react as police fire tear gas in the Kowloon area of Hong Kong, Monday, November 18. Hide Caption 24 of 160 Photos: Hong Kong unrest Firefighters put out a burning car set on fire by protesters near Hong Kong Polytechnic University in the Tsim Sha Tsui district on November 18. Hide Caption 25 of 160 Photos: Hong Kong unrest Police in riot gear move through a cloud of smoke as they detain a protester at the Hong Kong Polytechnic University in Hong Kong on November 18. Police have attempted to clear the university , which has been occupied by protesters for days as a strategic protest base. Hide Caption 26 of 160 Photos: Hong Kong unrest Police fire tear gas as protesters attempt to leave Hong Kong Polytechnic University via a bridge on November 18. Hide Caption 27 of 160 Photos: Hong Kong unrest A member of the police clashes with a protester at the Hong Kong Poytechnic University on November 18. Hide Caption 28 of 160 Photos: Hong Kong unrest Protesters use a rope to lower themselves from a pedestrian bridge to waiting motorbikes to escape from police at Hong Kong Polytechnic University on November 18. Hide Caption 29 of 160 Photos: Hong Kong unrest A protester throws an umbrella onto a fire at the barricaded main entrance of Hong Kong Polytechnic University on November 18. Hide Caption 30 of 160 Photos: Hong Kong unrest An anti-government protester is detained at Hong Kong Polytechnic University on November 18. Hide Caption 31 of 160 Photos: Hong Kong unrest An anti-government protester is showered down by volunteer medical workers after he was soaked by a police water cannons firing pepper spray-infused water at Hong Kong Polytechnic University on November 18. Hide Caption 32 of 160 Photos: Hong Kong unrest Riot police fire tear gas and rubber bullets as protesters attempt to leave Hong Kong Poytechnic University on November 18. Hide Caption 33 of 160 Photos: Hong Kong unrest A protester prepares to shoot an arrow during a confrontation with police. Hide Caption 34 of 160 Photos: Hong Kong unrest Police use a water cannon outside the Hong Kong Polytechnic University. Hide Caption 35 of 160 Photos: Hong Kong unrest A protester throws a Molotov cocktail at police on November 17. Hide Caption 36 of 160 Photos: Hong Kong unrest Protesters use a catapult to fire bricks at the police from inside the Hong Kong Polytechnic University on November 17. Hide Caption 37 of 160 Photos: Hong Kong unrest A woman tries to hold back riot police from approaching the Hong Kong University in Hong Kong on Saturday. Hide Caption 38 of 160 Photos: Hong Kong unrest Protesters train to throw Molotov cocktails into a swimming pool on the campus of the Hong Kong Polytechnic University on November 14. Hide Caption 39 of 160 Photos: Hong Kong unrest Protesters walk past barricades of bricks on a road near the Hong Kong Polytechnic University on November 14. Hide Caption 40 of 160 Photos: Hong Kong unrest Demonstrators gather during a lunchtime protest in the financial district of Hong Kong on November 14. Hide Caption 41 of 160 Photos: Hong Kong unrest A protester releases a flaming arrow to light a barricade at The Chinese University of Hong Kong (CUHK), Wednesday, November 13. Hide Caption 42 of 160 Photos: Hong Kong unrest A Molotov cocktail, a gas mask and a yellow construction helmet are placed upon a bust of late hotel tycoon Hui Yeung Shing at the campus of The Chinese University of Hong Kong on November 13. Hide Caption 43 of 160 Photos: Hong Kong unrest A fire is seen at a Mass Transit Railway (MTR) station during a demonstration at The Chinese University of Hong Kong on November 13. Hide Caption 44 of 160 Photos: Hong Kong unrest Students attempt to clear tear gas canisters fired by riot police onto a sports track during a confrontation at the Chinese University in Hong Kong on Tuesday, November 12. Hide Caption 45 of 160 Photos: Hong Kong unrest A man is detained during a protest at the Chinese University of Hong Kong on November 12. Hide Caption 46 of 160 Photos: Hong Kong unrest Students block an escalator with chairs in an attempt to hamper police at the University of Hong Kong on November 12. Hide Caption 47 of 160 Photos: Hong Kong unrest A protester is detained in the Central District of Hong Kong on November 11. Hide Caption 48 of 160 Photos: Hong Kong unrest People react after tear gas was fired by police during a protest in Hong Kong's Central District on November 11. Hide Caption 49 of 160 Photos: Hong Kong unrest Riot police face off with protesters at an entrance of a shopping mall during a demonstration on November 10. Hide Caption 50 of 160 Photos: Hong Kong unrest A man is helped by a volunteer medic after police used pepper spray during a demonstration on November 10. Hide Caption 51 of 160 Photos: Hong Kong unrest Students of the Hong Kong University of Science and Technology (HKUST) participate in a march on November 8, after hospital officials confirmed the death of student Chow Tsz-lok , 22. Police say Chow, a computer sciences student at HKUST, fell from the third floor to the second floor of a parking garage in the residential area of Tseung Kwan O in the early hours of November 4. Hide Caption 52 of 160 Photos: Hong Kong unrest A person places a flower at a memorial for 22-year-old Hong Kong university student Chow Tsz-lok on November 8. Hide Caption 53 of 160 Photos: Hong Kong unrest Students in gas masks are seen during a graduation ceremony at the Chinese University of Hong Kong on Thursday, November 7 in Hong Kong. Hide Caption 54 of 160 Photos: Hong Kong unrest Firefighters stand outside the offices of China's Xinhua News Agency after its windows were damaged by protesters in Hong Kong on Saturday, November 2. Hong Kong riot police fired multiple rounds of tear gas and used a water cannon Saturday to break up a rally by thousands of masked protesters demanding autonomy after Beijing indicated it could tighten its grip on the Chinese territory. Hide Caption 55 of 160 Photos: Hong Kong unrest Richard Chan, a candidate for the district council elections, reacts after being pepper-sprayed by police in Hong Kong on November 2. Hide Caption 56 of 160 Photos: Hong Kong unrest Thousands of black-clad masked protesters streamed into Hong Kong's central shopping district for another rally on November 2. Hide Caption 57 of 160 Photos: Hong Kong unrest A person dressed as President Donald Trump waves an American flag on a street in Hong Kong on Thursday, October 31, 2019. Hong Kong authorities braced as pro-democracy protesters urged people on Thursday to celebrate Halloween by wearing masks on a march in defiance of a government ban on face coverings Hide Caption 58 of 160 Photos: Hong Kong unrest A man dressed as the Joker for Halloween walks past police officers on October 31. Hide Caption 59 of 160 Photos: Hong Kong unrest Pro-democracy activist Joshua Wong (second from left) and Kelvin Lam (second from right) shout slogans as they meet the media outside the Legislative Council (LegCo) in Hong Kong on October 29, 2019, after Wong was barred from standing in an upcoming local election. Hide Caption 60 of 160 Photos: Hong Kong unrest A protester throws a tear gas canister on October 27 in Hong Kong. Hide Caption 61 of 160 Photos: Hong Kong unrest A couple wearing Guy Fawkes masks watch a rally at Chater Garden in Hong Kong on October 26. Hide Caption 62 of 160 Photos: Hong Kong unrest Protesters start a fire in front of the MTR station during demonstration on October 27. Hide Caption 63 of 160 Photos: Hong Kong unrest Tear gas smoke is seen exploding over reporters during an anti-government protest in Mong Kok district in Hong Kong on October 27. Hide Caption 64 of 160 Photos: Hong Kong unrest High school students take part in a human chain rally outside Kowloon park in Hong Kong on October 25. Hide Caption 65 of 160 Photos: Hong Kong unrest Police fire blue dye toward protesters in Hong Kong on Sunday, October 20. Blue dye can be used to stain and identify masked protesters. Hide Caption 66 of 160 Photos: Hong Kong unrest A pro-democracy protester is arrested by police on October 20. Hide Caption 67 of 160 Photos: Hong Kong unrest Pro-democracy lawmakers protest as Hong Kong Chief Executive Carrie Lam delivers a speech at the Legislative Council on Wednesday, October 16. Lam's annual policy address ended in chaos as pro-democracy lawmakers repeatedly disrupted her speech and heckled her with calls to honor the demands of anti-government protesters. Hide Caption 68 of 160 Photos: Hong Kong unrest A protester shoots a basketball at a poster of Lam during a rally on Tuesday, October 15. Hide Caption 69 of 160 Photos: Hong Kong unrest Protesters set fire to a Bank of China branch on Sunday, October 13. It was the 19th consecutive weekend of anti-government protests in Hong Kong. Hide Caption 70 of 160 Photos: Hong Kong unrest Protesters use the lights on their phones during a rally in central Hong Kong's business district. Hide Caption 71 of 160 Photos: Hong Kong unrest A protester attempts to break a tourist bus window on October 13. Hide Caption 72 of 160 Photos: Hong Kong unrest Protesters wearing masks in defiance of a recently imposed ban gather at a shopping mall on October 13. Hide Caption 73 of 160 Photos: Hong Kong unrest Supporters surround a police bus carrying political activist Edward Leung as it leaves the High Court in Hong Kong on Wednesday, October 9. Several hundred masked protesters gathered at Hong Kong's High Court for the appeal hearing of Leung, who was sentenced to six years in prison for his part in a violent clash with police. Hide Caption 74 of 160 Photos: Hong Kong unrest A woman is treated after police fired tear gas to disperse protesters in the Mong Kok district of Hong Kong on October 7. Hide Caption 75 of 160 Photos: Hong Kong unrest Pro-democracy protesters gather in a shopping mall on October 7. Hide Caption 76 of 160 Photos: Hong Kong unrest Rescue personnel check the bottom of a taxi after the driver allegedly drove onto the pavement, hitting protesters in Hong Kong on October 6. Hide Caption 77 of 160 Photos: Hong Kong unrest A China Construction Bank is seen vandalized in the Causeway Bay area of Hong Kong on October 6. Hide Caption 78 of 160 Photos: Hong Kong unrest Pro-democracy protesters set fires in the street in the Causeway Bay area. Hide Caption 79 of 160 Photos: Hong Kong unrest People protest the ban against masks on Saturday, October 5. Hide Caption 80 of 160 Photos: Hong Kong unrest An anti-government protester stands near a fire on Friday, October 4. Hide Caption 81 of 160 Photos: Hong Kong unrest Protesters move a statue depicting a protester armed with gas mask, helmet and umbrella on the streets of Hong Kong on October 4. Hide Caption 82 of 160 Photos: Hong Kong unrest Protesters set a fire at a China Construction Bank. Hide Caption 83 of 160 Photos: Hong Kong unrest Protesters spray paint slogans at the entrance to a tunnel on October 4. Hide Caption 84 of 160 Photos: Hong Kong unrest A store is in shambles after being vandalized by protesters. Hide Caption 85 of 160 Photos: Hong Kong unrest Pro-democracy demonstrators hold up their hands to symbolize their five demands during a rally on October 4. Hide Caption 86 of 160 Photos: Hong Kong unrest Protesters throw petrol bombs at the gate to the Tsuen Wan police station on Wednesday, October 2. Hide Caption 87 of 160 Photos: Hong Kong unrest Schoolmates of a student who was shot in the chest by police place their hands on their chests during a protest on October 2. Hide Caption 88 of 160 Photos: Hong Kong unrest A young protester was shot Tuesday, October 1, as violent protests erupted across Hong Kong on the 70th anniversary of the People's Republic of China. The incident marked a major escalation in violence that could galvanize the protest movement in Hong Kong. Hide Caption 89 of 160 Photos: Hong Kong unrest Police detain an anti-government protester on October 1. Thousands of black-clad protesters marched in central Hong Kong as part of multiple pro-democracy rallies. Hide Caption 90 of 160 Photos: Hong Kong unrest Police tackle and arrest pro-democracy protesters during clashes on October 1. Hide Caption 91 of 160 Photos: Hong Kong unrest A protester is seen carrying rocks on a street on October 1. While events in Beijing were being held to mark the 70th anniversary of the founding of the People's Republic of China, demonstrators rallied throughout Hong Kong. Hide Caption 92 of 160 Photos: Hong Kong unrest Protesters react after police fired tear gas near the central government offices in Hong Kong's Admiralty area on October 1. Hide Caption 93 of 160 Photos: Hong Kong unrest Pro-democracy protesters form a "Pepe the Frog" themed human chain on Monday, September 30. Hide Caption 94 of 160 Photos: Hong Kong unrest A man is detained by Hong Kong police during a protest in the Causeway Bay shopping district on Sunday, September 29. Hide Caption 95 of 160 Photos: Hong Kong unrest Bus passengers look at a burning barricade lit by pro-democracy protesters in front of the Mong Kok police station on Sunday, September 22. Hide Caption 96 of 160 Photos: Hong Kong unrest Pro-democracy protesters sing songs and chant slogans during a rally inside a shopping mall on September 22. Hide Caption 97 of 160 Photos: Hong Kong unrest A pro-China supporter, center, is escorted by police after confronting journalists in Hong Kong on September 15. Hide Caption 98 of 160 Photos: Hong Kong unrest Pro-government and anti-government supporters chant against one another at a shopping mall in Hong Kong on Friday, September 13. The sign translates to "Stop violence and curb chaos; safeguard Hong Kong." Hide Caption 99 of 160 Photos: Hong Kong unrest Demonstrators hold up their cell phone lights as they form a human chain at the Peak, a tourist spot in Hong Kong, on September 13. Hide Caption 100 of 160 Photos: Hong Kong unrest Police escort an injured man after he attacked protesters outside Prince Edward station in Hong Kong on Friday, September 6. Hide Caption 101 of 160 Photos: Hong Kong unrest Protesters burn paper money to pay their respects to injured protesters. Hide Caption 102 of 160 Photos: Hong Kong unrest Protesters prepare to clash with police outside the Mong Kok police station on September 6. Hide Caption 103 of 160 Photos: Hong Kong unrest A protester is detained by police at the Po Lam Mass Transit Railway station on Thursday, September 5. Hide Caption 104 of 160 Photos: Hong Kong unrest A man watches televisions at a store in Hong Kong as Chief Executive Carrie Lam announces the withdrawal of the extradition bill on Wednesday, September 4. Hide Caption 105 of 160 Photos: Hong Kong unrest A woman gets emotional on September 4 while paying her respects to protesters who were injured a few days earlier. Hide Caption 106 of 160 Photos: Hong Kong unrest Demonstrators travel through a railway station during a rally on Tuesday, September 3. Hide Caption 107 of 160 Photos: Hong Kong unrest Students wearing gas masks and helmets hold a banner that reads "five major demands are indispensable" at St. Francis' Canossian College in Hong Kong. Hide Caption 108 of 160 Photos: Hong Kong unrest Protesters gather in the bus terminal at Hong Kong International Airport on Sunday, September 1. Hundreds of pro-democracy activists attempted to block transport routes to the city's airport. Hide Caption 109 of 160 Photos: Hong Kong unrest A passenger walks to the airport on September 1 as pro-democracy protesters blocked a road outside the airport. Hide Caption 110 of 160 Photos: Hong Kong unrest A protester uses a slingshot outside the Central Government Complex during clashes with police on Saturday, August 31. Thousands of pro-democracy protesters held an anti-government rally one day after several leading activists and lawmakers were arrested in a sweeping crackdown. Hide Caption 111 of 160 Photos: Hong Kong unrest Protesters light a Molotov cocktail on August 31. Hide Caption 112 of 160 Photos: Hong Kong unrest Protesters take cover as policemen fire blue-colored water on them. Blue dye can be used to stain and identify masked protesters. Hide Caption 113 of 160 Photos: Hong Kong unrest A surveillance camera is covered with white paint during protests. Hide Caption 114 of 160 Photos: Hong Kong unrest An overhead view shows protesters reacting after police fired tear gas on August 31. Hide Caption 115 of 160 Photos: Hong Kong unrest Pro-democracy activists Agnes Chow and Joshua Wong speak to the media after they were released on bail at the Eastern Magistrates Courts on Friday, August 30. They were arrested earlier the same day in a dragnet across Hong Kong. Hide Caption 116 of 160 Photos: Hong Kong unrest Protesters clash with police after a rally in Hong Kong's Tsuen Wan district on Sunday, August 25. It was one of the most violent nights seen in Hong Kong since mass protests began in June. Hide Caption 117 of 160 Photos: Hong Kong unrest A police officer aims a gun in front of a protester on August 25. Hide Caption 118 of 160 Photos: Hong Kong unrest Some protesters shine laser pointers at police lines on August 25. Hide Caption 119 of 160 Photos: Hong Kong unrest Protesters pick up bricks to be used as projectiles on August 24.

Hide Caption 120 of 160 Photos: Hong Kong unrest Police retreat after clashing with protesters on August 24. Hide Caption 121 of 160 Photos: Hong Kong unrest Cell phones shine from the top of Lion Rock on August 23. Hide Caption 122 of 160 Photos: Hong Kong unrest Protesters march under umbrellas on Sunday, August 18. Hide Caption 123 of 160 Photos: Hong Kong unrest Tens of thousands of protesters showed up in the streets on August 18. Hide Caption 124 of 160 Photos: Hong Kong unrest A protester participates in a march on Saturday, August 17. His eye is covered with red gauze, referencing a woman who was allegedly shot in the eye with a beanbag round during clashes between protesters and police. Hide Caption 125 of 160 Photos: Hong Kong unrest Protesters point lasers at the Sham Shui Po police station on August 14. Hide Caption 126 of 160 Photos: Hong Kong unrest A police officer falls over an airport luggage trolley during a scuffle with pro-democracy protesters on Tuesday, August 13. For two days, protesters flooded the airport. Check-ins were suspended and dozens of outgoing flights were canceled. Hide Caption 127 of 160 Photos: Hong Kong unrest A traveler passes her luggage to security guards as she tries to enter the departures gate. Hide Caption 128 of 160 Photos: Hong Kong unrest A display board shows canceled flights on August 13. Hide Caption 129 of 160 Photos: Hong Kong unrest Medics look after a woman who received a facial injury during clashes on Sunday, August 11. Hide Caption 130 of 160 Photos: Hong Kong unrest A pro-democracy protester is held by police outside the Tsim Sha Tsui police station on August 11. Hide Caption 131 of 160 Photos: Hong Kong unrest Police fire tear gas at protesters during a demonstration in the Wong Tai Sin District on Monday, August 5. Hide Caption 132 of 160 Photos: Hong Kong unrest A train passenger gestures toward a protester, right, who was preventing the doors of a train from closing on August 5. The protester was trying to disrupt Hong Kong's morning rush-hour commute. Hide Caption 133 of 160 Photos: Hong Kong unrest A man comforts his pregnant wife near a train platform after protesters blocked the train doors on August 5. Hide Caption 134 of 160 Photos: Hong Kong unrest A protester stands in tear gas during a confrontation with police in the early hours of Sunday, August 4. Hide Caption 135 of 160 Photos: Hong Kong unrest A Chinese flag floats in water after it was thrown by protesters during a demonstration on Saturday, August 3. Hide Caption 136 of 160 Photos: Hong Kong unrest Members of Hong Kong's medical sector attend a protest in Edinburgh Place on Friday, August 2. Hide Caption 137 of 160 Photos: Hong Kong unrest The emblem on the China Liaison Office is protected by plexiglass during a demonstration on Sunday, July 28. Hide Caption 138 of 160 Photos: Hong Kong unrest A protester flees from baton-wielding police in the Yuen Long district of Hong Kong on Saturday, July 27. Hide Caption 139 of 160 Photos: Hong Kong unrest A protester looks through umbrellas during the clashes with police on July 27. Hide Caption 140 of 160 Photos: Hong Kong unrest Travelers watch as protesters rally at Hong Kong's international airport on Friday, July 26. Hide Caption 141 of 160 Photos: Hong Kong unrest Protesters clash with police on Sunday, July 21. Hide Caption 142 of 160 Photos: Hong Kong unrest Masked men in white T-shirts are seen after attacking anti-extradition bill demonstrators at a train station in Yuen Long. Hide Caption 143 of 160 Photos: Hong Kong unrest Medical workers help a protester affected by tear gas on July 21. Hide Caption 144 of 160 Photos: Hong Kong unrest The office of pro-Beijing lawmaker Junius Ho was trashed by protesters in Hong Kong's Tsuen Wan district. Hide Caption 145 of 160 Photos: Hong Kong unrest Police officers use pepper spray to disperse protesters after a rally in the Sheung Shui district on Saturday, July 13. Hide Caption 146 of 160 Photos: Hong Kong unrest A demonstrator sprays paint inside a chamber at Hong Kong's Legislative Council building, where protesters forced their way in on Monday, July 1. Hide Caption 147 of 160 Photos: Hong Kong unrest A protester smashes a window of the Legislative Council building. Hide Caption 148 of 160 Photos: Hong Kong unrest Columns of sunlight are cast on a crowd during the march on July 1. Hide Caption 149 of 160 Photos: Hong Kong unrest Helicopters carrying the flags of China and Hong Kong fly over demonstrators on July 1. Hide Caption 150 of 160 Photos: Hong Kong unrest A police officer uses pepper spray during a clash with protesters on July 1. Hide Caption 151 of 160 Photos: Hong Kong unrest A protester wearing a T-shirt with the word "revolution" walks past an inscription on a road that reads "Long Live HK." Hide Caption 152 of 160 Photos: Hong Kong unrest Police detain protesters near the government headquarters in Hong Kong on July 1. Hide Caption 153 of 160 Photos: Hong Kong unrest An overhead view shows thousands of protesters marching through a Hong Kong street on Sunday, June 16. Hide Caption 154 of 160 Photos: Hong Kong unrest Protesters run after police fired tear gas on Wednesday, June 12. Hide Caption 155 of 160 Photos: Hong Kong unrest By the morning of June 12, tens of thousands of mainly young people had arrived in the area, blocking streets and bringing central Hong Kong to a standstill. Hide Caption 156 of 160 Photos: Hong Kong unrest A demonstrator holds a sign during the June 12 rally. Hide Caption 157 of 160 Photos: Hong Kong unrest Police officers charge toward protesters during clashes on Monday, June 10. It was a continuation of protests that started the day before. Hide Caption 158 of 160 Photos: Hong Kong unrest Protesters on June 9 waved placards and wore white -- the designated color of the rally. "Hong Kong, never give up!" some chanted. Hide Caption 159 of 160 Photos: Hong Kong unrest Students wear chains during a demonstration on Saturday, June 8. Hide Caption 160 of 160

Before this year, pro-democracy protesters had peacefully marched each year on July 1 to mark the occasion.

"Protest is ingrained in the Hong Kong psyche. It's just a very normal thing to do," said Leslie, a 24-year-old protester and former English teacher. Leslie isn't her real name. She asked that CNN change it due to fears of reprisals.

In 1997, 2047 was a long way off for a teenager. They'd likely be retired by then. But Jim and Leslie will be in their 40s and 50s, respectively. "The future of Hong Kong really depends on the next few months, maybe the next few years, and how this movement pans out," Leslie said.

With that in mind, more than 500,000 turned out for this year's July 1 rally which begins at Victoria Park each year, according to organizers' estimates

Yet that's not where Jim and his team went. They met in Admiralty, outside the government's headquarters.

Calvin was already there by the time Jim arrived. The 18-year-old university student had spent the night sleeping on the ground nearby, with only a power bank to charge his phone and the clothes on his back. He wanted to be one of the first protesters there.

Protesters stand behind barricades outside the government headquarters the morning of July 1.

As the day went on, thousands more arrived.

People dressed in black and with masks covering their faces began pulling railings from the sidewalks to use as barricades. Some started to dig up bricks from the walkways. Calvin said that at about 2 p.m., a few proposed breaking into the government's legislative complex, known as LegCo.

At first, Calvin didn't think it was a good idea. His instinct was to push back against violence and destruction. And he didn't think the public would support it.

Neither did Jim. He didn't think violence was the answer.

"I've never seen this kind of stuff before," he said he thought at the time.

But both ended up doing what teenagers often do. They followed their friends.

"They're still my teammates," Jim said. "Whatever they do, I won't walk away."

Some of Calvin's friends were at the front, trying to break the glass doors leading into LegCo. He chose a middle ground: stand guard with an umbrella as other protesters smashed the doors with makeshift battering rams.

Protesters attempt to break a window at the government headquarters in Hong Kong on July 1.

Police standing inside the government headquarters look at protesters who tried to smash their way into the building.

With every violent push, the protesters chipped away at the barriers standing in their way. A handful of police officers stood on the other side of the glass. They warned people to stop or they would use force.

Protesters smash glass doors and windows to break into the parliament chamber of Legislative Council Complex on July 1.

By 9 p.m., the crowd finally made it inside. The police had vanished. Hundreds of protesters stormed in, cheering, waving their hands and celebrating their victory.

Then they vandalized everything in sight. They shattered more glass doors. They destroyed computers. They tore down portraits. They spray-painted "HK Gov f**king disgrace" on the wall.

"Liberate Hong Kong, the revolution of our time," they chanted.

Many thought protesters went too far by ransacking government property. Hong Kong is famously clean, efficient and safe. It boasts one of the world's lowest violent crime rates. Wanton destruction, mob violence and that level of vandalism are incredibly rare.

But as Calvin set foot in the building, he said he felt inspired.

With a successful strike at the symbolic heart of Hong Kong's unelected leader, Carrie Lam, Calvin thought the protesters were able to make an important point -- that "the government has already (sic) lose its legitimacy."

Once they reached the building's second floor, some started battering the entrance to the legislative chamber. It took them 30 minutes to get in. Once inside, one protester ripped apart a copy of the Basic Law, which acts as Hong Kong's mini-constitution. Another climbed up and spray-painted the city's emblem in black. Then they erected the British colonial flag.

Chaotic scenes inside LegCo.

Jim stayed inside for about 45 minutes, helping those who were spraying some of the graffiti that would become symbols of the protesters' anti-government fury. Then news that police had warned of an impending clearance operation circulated through LegCo, which was trashed by this point.

"Everyone was scared," Jim said.

Protesters like Jim left on their own terms. But his team learned on Telegram that four protesters had stayed. So Jim and his friends chose to join hundreds of others who went back inside to convince those who remained to leave.

Everyone departed minutes before riot police arrived, firing tear gas toward the retreating crowd.

Jim felt like he belonged. At that moment, strangers felt like family.

"Even though we don't know each other, we have the same goal ... we can't leave anyone behind," Jim said.

"I nearly cried because it felt very touching."

Police fire tear gas at protesters near the government headquarters on July 2.

Joining the fight

Bobo watched the events of July 1 and June 12 unfold from Canada, where she was attending university.

The 20-something Hong Kong native had a cute little dog and hoped to stay in the country once she graduated. Maybe she'd teach children. For now, she liked to grab drinks with friends at night and play bar games. Darts was one of her favorites.

But she was enraged watching police fire rubber bullets at protesters.

"I cannot just study overseas without coming back to join this fight," she recalled thinking.

So in early July, Bobo left her beloved toy poodle with a friend and booked a ticket home to Hong Kong. She began administering a group on Telegram called Bobo, which means "baby" in Cantonese, and grew it into one of the biggest and most reliable Hong Kong protest channels -- with nearly 30,000 members to date.

On the group, she sends regular updates about gatherings, police movements and other real-time news. She asked that CNN not use her real name and just refer to her as Bobo, fearing that police would target her.

Bobo supported the protesters who stormed LegCo on July 1. She called them heroes.

Their actions, she said, were "a symbol to tell the others" that Hong Kongers would not accept the current government.

Bobo has a history of political activism. She -- and Calvin -- were both involved in the 2014 pro-democracy Umbrella Movement, when protesters took to the streets of Hong Kong seeking universal suffrage.

Those peaceful protests simply fizzled out without achieving any political change after the government waged a slow war of attrition. Many of the movement's top leaders were eventually jailed.

Calvin and Bobo both said they were angry after the so-called Umbrella Revolution ended. They had given peace a chance. Now it was time for something else, and many others agreed.

series of on-site surveys of protesters conducted in June by several Hong Kong-based academics found that about half of the respondents "believed that peaceful, rational and non-violent protest was no longer useful."

"More and more participants considered radical protests to be more effective in making the government heed public opinion," it said.

Edmund Cheng, a professor of political science at Hong Kong Baptist University and one of the report's authors, said the research shows that even those who aren't thrilled about violence aren't going to stand in others' way.

"They may not approve of the violent actions of a small group of radical protesters, they still consider them as working toward a common goal," Cheng said.

The vandalism at LegCo on July 1 was a landmark moment for Hong Kong and its young people. The stage was set, and the summer was about to get more violent.

People walk past signs and posters outside the government headquarters in Hong Kong on July 2.

Desperate and hopeless

As the weeks turned to months, protesters graduated from throwing water bottles and umbrellas at riot police to bricks and Molotov cocktails. Police said rioters threw as many as 100 petrol bombs during the final weekend of August.

Protesters frame militancy as a necessary evil. They say their violence is only directed toward police and government. It's a far cry from lethal force and is escalated only if police escalate first, they say.

A Molotov cocktail is thrown by protesters in August.

Bobo and other protesters say Molotov cocktails and fire barricades are used to delay authorities and help protesters hold a line as others flee.

"We use them for self-defense, to maintain a distance between ourselves and the police. We all knew that we would be beaten up heavily if police were to come over," Bobo said.

Some admit the violence has at times crossed a line.

On August 12 and 13 , protesters stormed Hong Kong's airport. Hundreds of flights were canceled and chaos ensued. Two mainland Chinese nationals were detained by a mob on the second day. They were accused of being undercover officers. The mob stopped first responders from getting one of the men to an ambulance after he appeared to lose consciousness. The second, who turned out to be a reporter for Chinese state media, was aggressively searched and then ziptied to a luggage cart.

Many protesters made an effort the next day to apologize, recognizing they may have erred.

"People are desperate, people are hopeless, so they want to try all the means possible that lead to victory," said Andy Chan, an independence advocate and the founder of the Hong Kong National Party (HKNP), which the government banned on national security grounds last year . Critics say the move was politically motivated.

"Things may turn ugly sometimes but the crowd is always be able to self correct," he said of the scenes at the airport.

Chan was arrested twice last month, first on charges of possession of offensive weapons and then for alleged protest-related offenses . He denied the weapons allegations in an interview with CNN before his second arrest.

His second arrest happened at the airport while he was on his way to a conference in Japan. Chan said he was then held 44 hours before being released on bail. He has not been formally charged and no court date has been set, but police are investigating the case.

Chan said that he believes it's time for protesters to fight back against what he and many believe are increasingly heavy-handed tactics by police.

"In the past few years, we have experienced the violence of the police. Many of us agreed that we need to self-defend against the police," he said.

Police say their actions this summer have been in response to illegal activity. Tear gas and rubber bullets, they say, are used to disperse riots or illegal gatherings. A senior Hong Kong police officer told reporters at a briefing last month that they do not use force unless protesters use violence.

Protesters set a fire on August 31.

Almost all the protesters who spoke to CNN said this summer has changed the way they feel about police. Nearly every one brings up the incident in the suburb of Yuen Long on July 21 , when police were accused of looking the other way while a mob beat up protesters and passersby at a subway station. Police said the delayed response was because the two officers responding to the scene "did not have protective gears" and were waiting for reinforcements.

Several said they now hated the police. Others spoke in even more vitriolic terms.

"When you go to school and you're very young, the teachers teach you that if you need help, you call the police," Jim said. "No one trusts the police anymore."

Leslie, the 24-year-old English tutor, expressed a similar sentiment. When it comes to violence, she said protesters will lose public support if they're seen as the ones escalating against police.

"Things that may be morally inappropriate may be necessary," she said.

"Nothing will change if the current situation continues."

Bobo went even further. "I will not cut ties with them even if someone kills a police officer," she said.

Bobo said that before this summer she trusted the police.

"But at this moment, they are worse than dogs. They are even worse than rats crossing the street," she said.

"Anyone with (a) conscience will not stay inside the police force. You are not a good person if you decide to stay."

The most extreme protesters want this to go further -- they want to take on the Chinese military. They're not scared by reports that the People's Armed Police, a paramilitary force, had been temporarily deployed across the border in Shenzhen. Nor are they worried about Beijing and Hong Kong sounding the alarm over "signs of terror."

They've embraced a philosophy of "if we burn, you burn with us," a phrase popularized by "The Hunger Games" books.

These attitudes worry extremism expert Brian Levin.

Levin, who runs the Center for Hate and Extremism at California State University San Bernardino, said using violence -- even as a limited and calculated tool -- can have dangerous consequences.

"When some expression of violence is tolerated, that can unravel quite quickly. And when it does, it gets worse for everybody," he said.

Graffiti outside Hong Kong's Tung Chung subway station reads "burn with us."

'It's just like a dream'

Bobo now goes to as many demonstrations as she can. Sometimes she's up until 3 a.m. or 4 a.m. keeping the Telegram channel up to date. She wakes up for work three hours later and goes to her desk job.

Nowadays, Bobo brings a will to protests should she be killed. In it, she calls on her fellow protesters to continue the fight.

"Every time when I go out, I worry that I may die," she said. "I worry about (losing my future), but I am more scared that Hong Kong will be lost."

Leslie, Jim and Calvin said they've been to most of the protests. All three say they're motivated not just by ideology, but by the camaraderie they find on the front lines. Protesters liken themselves to brothers and sisters in arms, fighting for freedom together despite not knowing one another. Many often say one day they hope they can take off their masks and embrace one another.

For now, Calvin said it's like he's living a double life. "I go to the protest, and it's just like a dream, and when I wake up, it just ends," he said.

Leslie quit her tutoring job to fully commit to the cause. When she's not at a demonstration, she's helping with the translation and publication of protest materials.

"I can't really remember what it was like in June now," she said.

For many protesters, the summer has taken an emotional toll. Leslie now goes to a demonstration expecting tear gas and rubber bullets. Much of the time, she said she's numb to the violence.

"But the amount of times I've broken down says I just haven't found the right outlet for expressing my emotions," she said.

Jim, the high school student, no longer fears taking on the police.

At a protest at the end of August, he said he found himself on the ground staring at a police baton after helping up a fellow protester who had fallen over.

A member of the Hong Kong police's Special Tactical Squad was standing over him, he recalled.

A police officer from the Special Tactical Squad, nicknamed the "raptors," arrests a protester on August 11.

These aren't your average police. They dress in black, head to toe, and it's their job to go in and aggressively pluck out protesters for arrest after riot police fire tear gas. The squad has earned a reputation for violence, so much so that they're known locally as "raptors."

As Jim locked eyes with this raptor, he vowed not to go down without a fight. Rioting convictions can carry up to 10 years in prison. He didn't want to spend his formative years behind bars.

"I just wanted to get away," he said.

An officer walks in the Tung Chung subway station on September 1.

First he went for the jugular. Jim said he grabbed the raptor's throat, only to find he was wearing protective neck gear.

So he went lower. Jim said he kicked the raptor in the groin, causing him to keel over in pain and giving the young protester enough time to make a run for it.

In the seconds he made his getaway, Jim said he saw a protester throw a Molotov cocktail.

People cheered. Police drew back, Jim said, effectively ensuring he was able to escape.

But that freedom wouldn't last.

Jim and several members of his team were arrested days later for possession of offensive weapons. Jim said all they had on them were a few laser pointers. Police have started classifying laser pointers as weapons because they've been used at demonstrations to distract officers and members of the media, but they can also blind people.

Jim called his arrest "unreasonable." He has since been bailed out.

The summer's events have surprised even Jim. In mere weeks, he transformed from apolitical student who just wanted practice first-aid to a passionate activist and frontline protester with a rap sheet.

"Before these events happened, I think actually I'm not quite important or political. Like, I'm just a student and I can't do anything on my own," he said.

"Now I know that everyone is very important, and when we have a lot of people joining together, we can be very powerful."