The scenes have become chilling, even in a Hong Kong that's now hardened from three months of clashes between protesters and police.

With demonstrations mostly outlawed, the same streets where millions once walked peacefully now see fires on the roadway and blood on the pavement.

This past weekend, an "illegal" march by church groups, seniors and students became a running battle between protesters and riot police, punctuated by Molotov cocktails and enveloped in clouds of tear gas.

Protests designed to block access to Hong Kong's international airport caused trouble for travellers and led to one transit station being thoroughly trashed by masked youths with spray paint and steel rods.

Demonstrators take cover during a protest in Hong Kong Saturday. Levels of violence have been rising. (Danish Siddiqui/Reuters)

But the images that shocked people the most came from a subway car. After ordering trains stopped, the police tactical squad (nicknamed "Raptors") raided the station looking for protesters on their way home.

Video shows them beating and pepper-spraying four young passengers who were neither questioned nor arrested at the scene, simply left cowering in a corner of the carriage. (Two were later arrested, after the public outcry.)

Witnesses later said it seemed like the officers were just lashing out at anyone they could out of anger and frustration.

Many called it exactly the kind of police abuse that needs to be investigated by an independent inquiry — one of the protesters' key demands. But authorities seemed to dismiss it as normal police work.

Hong Kong's Secretary for Security John Lee said the officers were just "upholding the law" and "trying to reduce the injuries and harm to everyone."

He insisted the police force is still "Asia's finest."

It's clear positions on both sides — police and protesters — have toughened, along with their strategies. And that's turned the political battle for greater democracy into a very real fight for control of the streets.

Young people like Jack are at the heart of it. He's 19, too afraid of police to give his last name, but not afraid to confront them on the streets. Every chance he gets.

"Sure, it's getting harder," he said through a broad face mask that covered all but his eyes, "but we will keep fighting."

Jack stood waiting for the next protest to begin, outfitted in full protest combat gear: yellow construction helmet, black T-shirt, gas mask and heat-resistant gloves to throw hot tear gas canisters back at the police.

Another young man, 17 year-old Morgan, sat on a curb nearby.

Passengers try to flee as riot police arrives, outside the terminals at Hong Kong International Airport on Sunday. (Anushree Fadnavis/Reuters)

"It's some kind of a last chance of Hong Kongers to stand for what we want: democracy," he said.

Significantly, even as the violence has increased and the actions more aggressive, Hong Kong's young people still seem to have the support of parents, teachers and many others who might be expected to condemn them.

This is our home, this is our city. Society simply cannot move on with this kind of confrontation." - Bonnie Leung, Civil Human Rights Front

This movement started as an effort to push the Hong Kong government to abandon a bill that could see anyone charged with a crime extradited to mainland China to face trial. Leader Carrie Lam reluctantly suspended work on the bill and declared it "dead," but she would not withdraw it entirely.

And since then, her government has mostly gone into hiding, refusing to discuss any other demands with protesters, including those aimed at expanding democratic rights and protecting freedoms in the face of greater control by the Beijing government.

Lam herself has only appeared in public occasionally to sternly condemn protesters and unequivocally support the police. Her private views seem less definitive, and even anguished.

Protesters build barricades outside the airport terminals Sunday. (Kai Pfaffenbach/Reuters)

In a leaked recording of a private speech she gave last week to Hong Kong businesspeople, she said she would "quit" if she could, but her backers in Beijing would not allow it.

And despite a steely posture that has been disliked and mocked in Hong Kong, Lam said privately she feels that "to have caused this huge havoc to Hong Kong is unforgivable," something she would have to apologize for "deeply."

She also told the group Beijing has "absolutely no plan" to intervene with People's Liberation Army troops, who have a garrison in the middle of Hong Kong. This has been a constant worry for residents — as well as world leaders and observers abroad — who remember China's bloody crackdown against protesters in Tiananmen Square 30 years ago.

More explicit threat

The fear has been stoked by Chinese propaganda, showing mainland police and troops training to attack people dressed just like Hong Kong's protesters and characterizing them as nothing more than a spoiled and violent mob. Political demands are never mentioned.

A weekend editorial in Beijing's state news service Xinhua made the threat even more explicit.

It said anyone who "dares to infringe" on China's national sovereignty or challenges the power of Beijing will "be held accountable." And it warned "the end is near" for the protests, without laying out when or how.

A barricade burns during a protest near the airport Sunday. (Anushree Fadnavis/Reuters)

For Bonnie Leung, that's exactly the wrong way to solve this standoff.

Leung is the vice-convenor of the Civil Human Rights Front (CHRF), a group that has organized the biggest peaceful rallies of these protests, drawing more than a million people to the streets three times — once, over two million.

'Making the problem worse'

CHRF's request for another peaceful march this past weekend was turned down, and Yeung suspects that pushed many young people to make their statement another way: through violence.

She also said excessive force by the police may be "making the problem worse," backfiring by making more protesters more radical.

After watching the scenes of police beating young people on the subway, "a lot of Hong Kong people feel the same desperation," Leung said.

"We are angry about the brutality of the police, but we have to find a way to solve that problem," she said, with tears in her eyes and a quiver in her voice. "Because this is our home, this is our city. Society simply cannot move on with this kind of confrontation."