On 1 February 1960, 17-year-old Franklin McCain and three black friends went to the whites-only counter at Woolworths in Greensboro, North Carolina and took a seat. The humiliation of growing up black in the south had left the teenage McCain contemplating suicide. Having spent the previous night chastising the older generation for their failure to effectively confront segregation, the four young men had talked themselves into an act that was brave, reckless, exhilarating and, ultimately, liberating.

“We wanted to go beyond what our parents had done,” McCain told me almost four decades later. “The worst thing that could happen was that the Ku Klux Klan could kill us … but I had no concern for my personal safety. The day I sat at that counter, I had the most tremendous feeling of elation and celebration. I felt that, in this life, nothing else mattered … If there’s a heaven, I got there for a few minutes. I just felt you can’t touch me, you can’t hurt me. There’s no other experience like it.”

Listening to David Hogg, the 18-year-old former high school student who became an internationally known gun-control campaigner after a gunman shot dead 17 students and staff and injured 17 others at his school in Parkland, Florida, reminds me of McCain’s account of his protest. Fearless, relentless, passionate, earnest and old beyond his years yet brimming with youthful intensity. A teenager who, having already entertained his own mortality, has become recklessly audacious and singlemindedly driven.

Will he go to college next year? “I don’t feel comfortable going to college until we have at least $50m to fund gun violence research annually,” he says. Has he had time to grieve? “I can’t sit back and grieve while so many people are dying.” What’s the difference between the gun control efforts he is involved in and previous attempts that have not succeeded? “We are young and we are not going to leave it to a generation of corrupt politicians to decide our future.”

Hogg has the interview manner of a person who is more used to answering questions than listening to them. It would be easy to lampoon him. But it would also be ungenerous. He is young, his sister lost four of her friends in the shooting, and he was unexpectedly thrust into the public eye. He is also dyslexic and didn’t learn to read until he was nine. His mother told New York magazine that the challenges of those early years account for his declarative manner. “He gets absorbed in his words because he’s been doubted so much,” she says. “He needs to overcompensate when he’s arguing.”

When I ask what side of his personality the media portrayals fail to catch he passes the phone to his two friends. “There’s a goofball side of him,” says one. “They portray him as a stern hard-arse – and he is sometimes. But that’s not who he is all the time.”

Hogg at a youth march in Massachusetts in August. Photograph: Katherine Taylor/EPA

At the beginning of the year, he wanted to be a journalist or an aerospace engineer. For the past eight months, thanks to a tragedy not of his making, he has become a high-profile figure in a media culture where certainty is valued far more than clarity or nuance. He was applying for colleges. Now he is being offered six- or seven-figure salaries by media outlets and nonprofit organisations and receiving invitations for paid speaking gigs at universities that rejected him.

Since he started speaking out about gun control, he has been the subject of several threats on his life and, at times, has been accompanied by a security detail. (Facts he would rather not discuss.)

Hogg divides his short life into before the shooting and after. Before: a debate team geek with a handful of friends. “I was not popular at all and I wasn’t an extrovert. And I’m still not: I’m an introvert, I like to keep to myself.” After: a constant media presence and tireless campaigner with more than 900,000 Twitter followers.

That transformative moment lasted just a few minutes. Nicholas Cruz, 19, arrived at the Stoneman Douglas high school at 2.19pm with an AR-15-style semi-automatic rifle and several magazines and soon started shooting indiscriminately. The shooting lasted six minutes. Before the hour was out, Cruz had left the school with fleeing students. He went to Walmart, Subway and McDonald’s.

The first time many of his fellow students met Hogg, the shooter was still at large and Hogg’s angular face was lit as though for a Hitchcock movie: a wide-eyed glare peering from a dark place. He had heard the gunfire and been herded, with several other students, into what looks like an unlit cupboard to hide. In the midst of this terror, he narrates the scene on his phone to an audience that has yet to exist. “Right now, we’re in a school,” he whispers, affecting the cadence of a war reporter. “An active shooter. It’s not a drill.” He goes on to interview fellow students before launching a political broadside: “The fact that school shootings have happened so much to the point that we need drills for them almost as much as fire drills is unacceptable. I call on legislators of this country to take action and stop this from happening.”

For Hogg, the shift to advocacy was not simply immediate, it was simultaneous. He went to school a nerd and turned himself a national advocate as the event was happening. A few days later, while the political class was still talking “thoughts and prayers”, his classmate Emma Gonzalez “called BS” on the entire establishment regarding gun control. Hogg and Gonzalez knew each other from astronomy club, where they worked together the year before on an experimental weather balloon. The vehemence with which they, and other students, protested against lax gun laws in the immediate wake of the shooting roused a dormant constituency.

When reporting for my book about all the children and teens shot dead in one random day in the US, I asked each family who lost a child an open-ended question: what did they think had made the tragedy possible? Not one mentioned guns. When I asked the more leading question, of what they thought about guns, most had an opinion: they were too easily accessible. They just didn’t think anything could be done about it. In the few weeks after Parkland, the learned hopelessness around the prospect of gun control seemed to have been replaced by a sense of urgency, militancy and indignation that had been sorely lacking. Hogg was not yet a teenager when the shootings at Sandy Hook happened in 2012. Neither he, nor his fellow students, had yet learned to be hopeless.

For the first time we heard the witnesses and the victims of the mass murder tell their own story

Hogg says one of the key reasons the shootings at Parkland produced a broader and bigger response than other school mass shootings was timing and agency. “We spoke up immediately after the shooting,” he says. “For the first time we heard the witnesses and the victims of the mass murder tell their own story. We spoke out against it in a particular way.”

The other, he says, is that those who were affected were relatively affluent and mostly white. “If our school had been in a different zip code, we wouldn’t have got the same coverage.” Hogg’s father was an FBI agent (and is a Republican) and his mother (a Democrat) is a teacher. How does he navigate the fact that he has become a prominent advocate in a cause that has a disproportionate impact on black and brown communities living in poverty? “I acknowledge it, in the first place,” he says. “I don’t know what it’s like to be discriminated against. I can empathise, but I can’t sympathise. So then I, literally and metaphorically, hand over the mic to someone who does.”

The uncompromising rhetoric after Parkland triggered a wave of protests. There were school walk outs that involved millions of students and die-ins outside the White House and elsewhere. Hogg was one of the speakers on March for Our Lives, a demonstration in Washington called by another Parkland student – the third-biggest demonstration in US history – that took place less than six months after the shooting.

The protest figureheads also drew significant opposition. Hogg and some of his fellow student leaders were accused, by the rightwing echo chamber, of being “crisis actors” – trained dramatists putting on a show for the cameras for political purposes. A rumour raced through the internet claiming that Hogg wasn’t even at the school when the shooting happened and that the video he put together was a fake.

Days after March for Our Lives, his public profile soared further as he faced down the ultra-conservative Fox News anchor Laura Ingraham, who mocked Hogg on Twitter after he was rejected by four colleges. Hogg hit back, calling on advertisers to boycott Ingraham’s show. Advertisers duly pulled out. Ingraham apologised. Hogg refused to accept her apology. The advertisers have stayed away – and her ratings have gone up.

From then until now, Hogg has barely stopped. He led a mass die-in at a supermarket chain that contributed to a Florida gubernatorial candidate who took money from the National Rifle Association (NRA). Over the summer, some survivors from Stoneman Douglas took a bus tour across the country – 75 cities over two months – in a bid to register young voters.

Hogg believes that the results in the recent US midterms, where he cast his first vote in a general election, speak for themselves. “We had the largest youth turnout in history,” he says. “We promoted youth engagement all over and had one of the largest protests in American history.” It is true that November saw a record number of young people vote in a midterm election. But it’s also true that, at around 31%, the number still lagged significantly behind all other age groups. At the time of writing, there have been 296 mass shootings – where more than one person was killed or wounded – since Parkland, 25 of which have been in Florida. And gun policy was the fourth most important issue for voters (after healthcare, immigration and the economy) even though there was a mass shooting in a synagogue 10 days before polling day. For all the hard work the activists had put into their home state, it wasn’t enough to tip the balance in Florida, where voters sent one gun-loving Republican to the Senate and another to the governor’s mansion. Hogg shifts register from advocate to politician, advising against impatience and frustration. “Change takes a lot of time,” he says. “We are not always going to be 100% successful.”

Hogg addresses protesters at a March for Your Lives rally outside the headquarters of gun manufacturer Smith & Wesson. Photograph: Steven Senne/AP

He believes the primary, if not sole, obstacle to change has been the main gun lobby, the NRA. The gun-control movement was cowered by them, he says. “Some [gun-control] organisations wouldn’t even talk about the NRA because they were afraid,” he says. “Democrats and Republicans were afraid of the NRA. We have to make it so that it pays for you to stand against the NRA and that you pay if you stand with the NRA.”

Meanwhile, the population at large has been duped by them, he says. “In the 50s, two thirds of Americans thought having a gun in your house made you less safe. Now, two thirds think it makes you more safe. That’s NRA propaganda. Their success has been in convincing people that they have no power to change anything.”

He believes the movement’s main task is not so much to change people’s minds as to make them hear and understand the case they are making. “They don’t understand what we stand for. They think we want to take away their guns, and we are not advocating taking guns away. A majority of people already believe in gun reform.”

That’s true. And yet Hogg’s reasoning seems to assign a little too much credit to the NRA and too little to the agency of American people. In 2013, after Sandy Hook, polling showed gun owners were almost twice as likely as non–gun owners to have contacted a public official about gun policy, and almost three times as likely to have donated to a group that takes a position on the issue. When the national narrative is underpinned by self-reliance, rugged individualism, masculinity, conquering, dominating, force and power, the NRA may simply be better positioned to tap into attachment to mythologies than any logical argument about “common-sense gun reform” made by the other side.

On the evening of the Parkland shooting, before the Twitter spat, Hogg went on Ingraham’s show. Just as she was drawing his segment to an end, he interjected: “Can I say one more thing to the audience? I don’t want this just to be another mass shooting. I don’t want this to be something that people forget.”

I put it to him that Parkland has not been forgotten. But that it has perhaps become another mass shooting that people remember, like Newtown or Columbine – a punctuation point in a story that doesn’t change. How is this possible? “People forget and they move on,” he says. “It says a lot about our country.”