The facts of the Parkland school shooting are by now so well branded on the national consciousness it barely requires recap: on Valentine’s Day 2018, a teenage gunman killed 17 students at Marjory Stoneman Douglas high school in six minutes; students documented their fear and disbelief in real time. Overnight, some became characters in the national battle over gun violence – known to millions as, depending on one’s slant, heroic crusaders against inaction, targets of rightwing trolls, or conspiracy theories’ “crisis actors”.

This owed in part to many of the students’ shellshocked refusal to let the Parkland shooting fade into the sickeningly familiar loop of American mass shootings amnesia, by taking interview after interview, posting frequently on social media, and organizing March For Our Lives (MFOL), the largest youth protest movement in American history. It was also a media fixation, ranging from well-meaning to intentionally destructive, to use a handful of children – mostly white, from an affluent every-suburb of Florida – as avatars for the bitter politicization of guns in the US.

It was an unfathomable amount for anyone, let alone a teenager, to handle – a burden explored in the documentary Us Kids which follows several March for Our Lives students turned activists over the course of 2018. “We were still kids, or just barely adults,” David Hogg, one of the most prominent activists, told the Guardian. “Most people don’t even know who they are at that point in life, or really don’t know who they are. And on top of all of that, we were having to grow up and mature live in front of cameras, which was just a lot.”

Directed by Kim Snyder, Us Kids captures the overwhelming, at times energizing pressure of the movement – the hope and the activists’ unbelievable momentum as internet-native commanders of attention in a hyper-connected media environment. It’s half a documentary of documentation, as the teens travel around the country and offer, again and again, evidence (be it emotional, statistical, or logical) for their argument that it does not have to be this way.

Us Kids is chiefly concerned with the weight of attention – its costs, inequality and real potential for more than lip-service change – on the Parkland group specifically and the generation of young people traumatized by gun violence. For participants such as X González (who announced their name change on the Tonight Show this week), Jaclyn Corin, Cameron Kasky and Hogg, there were magazine covers, cable news appearances, talkshows, galas, tens of thousands of followers on their personal social media accounts. Hogg himself appears in another documentary, ABC Film’s After Parkland, and plays a prominent role in Dave Cullen’s 2019 book Parkland, the definitive textual account of the March for Our Lives movement.

Snyder’s camera captures moments of teenage levity on the road – singing in a conference room, riding scooters in a parking lot. But the kids can rarely afford to be off-stage; Snyder’s is often one of many cameras recording Hogg or Gonzalez’s attempts to sincerely engage with other people – from combative second amendment stans to news media or well-meaning supporters – on a topic they have learned at traumatic rocket speed, with a bunch of strangers’ iPhone cameras in their faces. It’s no surprise that, looking back on the tour in the film, González reflects: “I was a broken person by the end of all that.”

The film shows “that we really are just kids”, said Hogg, now 21 and a student at Harvard. “It makes us human, and I think that’s so important for people to see, no matter if they absolutely despise us or love us. Because ultimately, that’s the cost of this, no matter what your beliefs are. If you’re the hardest, hardcore rightwing pro-second amendment person or the most anti-gun, whatever, kids are still dying every day.”

Before 2018, Snyder had spent years working closely with families shattered by the shooting at Sandy Hook elementary school in 2012 for her 2016 film Newtown. So when students immediately channeled their trauma and hurricane of emotions into unflinching political action, “I wasn’t surprised,” she said. “I knew that there was this whole generation who in Newtown were first-graders and were now middle-schoolers that were just fed up and angry and scared.”

Still, when she incidentally encountered MFOL activists at the Florida state capitol in 2018, “I looked out and I saw this sort of sea of young people, and something felt really different,” she said.

Snyder hoped to capture the energy of the movement both for posterity and as a tool to activate coming-of-age voters, but it took awhile to build trust with teenagers whose trauma was by then plastered across national media to various ends. “We’ve been used so many times, and in some ways even emotionally or mentally abused by the media to get certain reactions, that it was really hard to trust anyone with a camera,” Hogg said.

Both Snyder and Hogg recalled conversations about boundaries – time and space without cameras, discussion over what and who would be included in the film, and collaboration over how to structure a documentary that could reach youth voters. “I knew, and I think the rest of the students knew on the bus and everything, that what wasn’t going to work was turning this into some kind of grotesque reality TV show-style situation,” said Hogg. “Because on tour and to this day, we’re still processing everything that happened.”

There is, amid the town halls and rallies, space for quiet healing. Us Kids spends significant time with survivor Sam Fuentes, who was shot twice in the leg and witnessed the death of her friend, Nicholas Dworet. Wry and remarkably lucid about the sensations of PTSD, Fuentes provides a very partial glimpse at aftermath: befriending, over the course of the year and occasionally on camera, Dworet’s younger brother Alex, and overcoming literally choking terror onstage (at the march, at the Pen America gala in New York) to finish a speech.

For the Parkland students on tour, traveling across the country was a learning process in intersectional activism. Bria Smith, a black youth activist from Milwaukee, discusses both the frustration with white American apathy toward black victims of endemic gun violence, and the promise felt by partnering with March for Our Lives, which includes in its list of demands for the Biden-Harris administration’s $1bn in funding for evidence-based community intervention programs which address endemic gun violence in 40 cities.

“The reason why shootings don’t happen in Parkland on a daily basis isn’t because we have stronger gun laws than the rest of the country, it’s because we have more resources,” Hogg said. “And that’s one of the harder conversations that people don’t want to have about this issue: the reason why we have gun violence in our country is of course in part because of our lack of gun laws, but it’s also because of systemic, massive inequality.”

Three years since the first March For Our Lives, there would be reason enough to feel hopeless – a record-breaking 19,223 gun violence deaths last year, 10 killed by a man at a grocery store in Boulder, Colorado, in March, followed less than a week later by another eight killed by a man targeting Asian American women at massage parlors around Atlanta. But there’s the long game – record youth voter turnout in 2018 and 2020, in no small part due to Parkland students’ activism, or the election of MFOL-supported representative Lucy McBath, a black woman who lost her son to gun violence, in Georgia. And crucially, the once-unfathomable weakening of the National Rifle Association (NRA), now mired in bankruptcy and a federal lawsuit over financial mismanagement.

“I think we’re going to outlast them,” said Hogg of the opposition, and the NRA in particular. “The seeds that we planted across the country ... they’re eventually, I imagine, going to have young people running for office.”

• Us Kids is now out in cinemas and to rent digitally in the US with a UK date to be announced