Ariana Lopez spent over two hours huddled inside a storage closet with 60 other people.

Half stood, while the others sat on the floor of the closet, which measured no more than five square metres, as a gunman opened fire on students and staff at Marjory Stoneman Douglas High School in Parkland, Florida.

"It was absolute fear," said 17-year-old Lopez as she recalled the deadly February 14 shooting.

"When the gunshots were going on, you could almost see it reverberating [on] the walls."

It's been just over a month since Nikolas Cruz, a former student at the school and the suspected attacker, admitted to carrying out the deadliest school shooting in modern US history.

Seventeen people were killed in the attack, including Helena Ramsay, one of Lopez's closest friends whom she had known since elementary school.

"She was one of those people you meet once in a lifetime that draws you to them and you want to spend as much time with them as possible before they leave," Lopez told Al Jazeera in a phone interview.

She said she only found out Ramsay had been killed around 3am on February 15, hours after the shooting had ended. Ramsay had shielded other students with her body and died instantly, Lopez said.

One of my closest friends since the fourth grade was ripped from me because of an absolute monster. But I have to say, I have never been prouder of her bravery to give up her life for others. I love you, Helena. And I will always be proud of you. https://t.co/2NTwyElgus — Ariana Lopez (@ArianaLopez_MSD) March 11, 2018

"We had told everybody she's in the hospital, she's okay and she's going to be fine," Lopez said.

"And then it kind of hit us like a train."

'A fair game'

As families and friends grapple with the death of their loved ones in the aftermath of the shooting, Parkland students and others have emerged as leaders of a nationwide movement calling for stricter gun control lawsin the US.

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On March 14, thousands of students and teachers staged 17-minute walkouts, one minute for each victim in Florida, "to protest Congress' refusal to take action on the gun violence epidemic plaguing our schools and neighbourhoods."

Students have urged politicians to reign in the National Rifle Association (NRA), a pro-gun lobby group that has made millions of dollars in campaign contributions to members of the US Congress and Senate.

Their calls to boycott groups that do business with the NRA have led dozens of hotel chains, car rental companies and other businesses to cut ties with the powerful gun lobby.

Students in Wisconsin will begin a four-day, 80km march from the state capital of Madison to Janesville, the hometown of Republican Congressman Paul Ryan, on March 24 to call for changes to US gun laws.

"This is an issue that affects every kid around the US and we wanted to help make a change," said Katie Eder, a co-leader of the "50 More Miles" march and a senior at Shorewood High School.

She said the students are specifically calling out Ryan since as the Republican speaker of the House he has the power to back legislation that would end gun violence.

"He's really someone who has really refused to acknowledge what's going on," Eder told Al Jazeera.

"We're bringing it to his hometown to say; 'Paul Ryan, you can't continue to ignore us.' We care about this issue and we're going to continue to fight," she said.

Under pressure to take action, the Florida legislature recently passed stricter gun control laws, which raised the minimum age for buying a firearm from 18 to 21. The same legislation also allows teachers to be armed in schools, which was widely criticised.

The US Department of Justice has formally proposed a measure to ban bump stocks, an addition that turns semi-automatic into fully automatic, machine-gun type weapons, and similar bans are being considered in several US states.

Families have started to organise in the memory of their loved ones, as well.

Manuel and Patricia Oliver, whose son, Joaquin, was killed in the Parkland shooting, recently formed a new organisation called Change the Ref to empower youth across the US to have their voices heard.

The name comes from an incident that happened during a high school basketball game shortly before the attack at Marjory Stoneman Douglas.

Joaquin - whom Javier Marin, a long-time family friend, described as "crazy about sports" - had been ejected from the game by a referee he felt was treating him and his teammates unfairly.

Marin said that once on the bench, Joaquin turned to his father, who also coached the team, and asked, "Well, are you going to do something?"

Manuel went to talk to the referee, but he did not get a clear answer.

He then realised that his team needed "to just find a fair game … and that's how Change the Ref came out", said Marin, referring to the influence US gun lobbyists yield on elected officials.

"It's a beautiful mission to keep the legacy of his son and some energy to be alive and keep going," Marin said of Manuel. "We want to follow the youth's message and Change The Ref only works to support their voice and their message."

'Beyond Parkland'

At first, Kenidra Woods prayed the video being shared on social media wasn't real.

Filmed by what appeared to be a student, it showed the panic and fear gripping the Parkland high school when shots first rang out on February 14.

"I was real heartbroken when I started seeing all this stuff. I heard about people dying … That's when I was like, 'I'm going to act on this'," Woods, who lives in St Louis, Missouri, told Al Jazeera.

Woods had already been active in the movement to get justice for Michael Brown, a black teenager who was shot multiple times by a white police officer and killed in 2014 in Ferguson, a suburb of St Louis.

Brown's killing sparked a nationwide protest movement against police brutality and anti-Black racism under the banner, Black Lives Matter.

"We still feel like we didn't get justice for that," said Woods, 17.

"I was just tired of it … I feel like that anger towards that situation [and] I'm just like, 'No'. This [Parkland shooting] was the straw that broke the camel's back."

With her classmates, Woods organised a walkout at her local high school on February 22 and she will be travelling to Washington, DC, to join the March for Our Lives rally against gun violence on March 24.

I march for my black brother who could've just lost his life to gun violence, my mom who was kidnapped at gun point with a gun held to her head, my aunt who was shot 6x left to die, and students from different walks of life who have been affected by this. Change is NOW. — therealkenidrawoods (@KenidraRWoods_) March 15, 2018

She said gun violence is omnipresent; recently, one of her classmates was killed along with his mother, after his stepfather shot them both and then turned the gun on himself.

"This is way beyond Parkland. It's not just about stopping gun violence at schools … we need to stop gun violence around the world, especially in the US," Woods said, adding that she fears for her older brother's safety every time he leaves the house.

"We face injustice as black people and I'm afraid because my brother has had encounters with police," she said.

"I feel like it [the Parkland shooting] also got real coverage because it was primarily white students.

"As a black girl in America, my voice is not as important in a way and that's why I'm speaking so loud [and] speaking so much … I've been speaking about this since Mike Brown and nothing was done."

'Kids in every community get gunned down'

Kyrah Simon, 17, was evacuated from a building at Marjory Stoneman Douglas with her classmates after the fire alarm sounded.

While at first she thought there might have been a fire or a bomb threat, she said she knew it was something more serious when a helicopter hovered overhead during the evacuation.

"I was in disbelief," Simon told Al Jazeera, about how she felt once she found out someone had shot her classmates.

Now, she said she's going through the many stages of grief, from disbelief to sadness and anger. "It's just ebbs and flows," she said.

Simon, who will travel to Washington, DC to join the March for Our Lives rally later this month, said she hoped the tragedy at her school could help "broaden the discussion about gun violence" in the US.

"It's not just about Parkland kids, or not just about the kids that perished; there [are] kids in every community that get gunned down in the streets and they don't get a story on the news," she said.

"At the march, I hope we're able to hear a lot of voices … Kids from Chicago, I can't wait to hear them speak. Baltimore, St Louis, more voices that we haven't heard before.

"With this situation, everybody deserves a platform to speak their truths."