Parkland is an affluent city of 30,000 people, 40 miles north of Miami on the edge of the Florida Everglades. Families once moved there for its safe neighbourhoods and good schools. One former mayor said life revolved around its open spaces and fields. It was also one of the safest cities in Florida – but that all changed on Valentine’s Day 2018 at 2.19pm.

That’s when 19-year-old Nikolas Cruz was dropped off by an Uber driver outside Marjory Stoneman Douglas High School, where he was once a student. Carrying a duffel bag and backpack, Cruz walked into a three-storey building on campus and set off a fire alarm. He pulled a Smith & Wesson M&P15 semi-automatic rifle – a weapon he’d purchased legally – out of one of the bags, and at 2.21pm began firing at students in the ground-floor corridor.

After the shooting, the Broward Sheriff’s Office would produce an animated timeline of Cruz’s movements inside the building. He’s represented by a black dot with a small line denoting his weapon; students are green dots, staff are blue. As Cruz’s bullets hit his victims, the colour of those dots change – yellow for the injured, purple for the dead.

Thirty seconds after Cruz first opened fire, three dots turn purple, representing three students he killed in a classroom doorway. He then injures another further down the corridor before turning and standing in the doorway of another classroom and firing, killing one and injuring three. It’s a rudimentary graphic but its simplicity echoes the ease and efficiency with which Cruz was able to cut short the lives of 17 people. By 2.27pm – just six minutes and 20 seconds – it’s all over and his avatar exits the building.

Marjory Stoneman Douglas High School shooting, 2018, 17 dead Florida school shooter Nikolas Cruz, 19, bought his rifle legally. A day after the massacre, a prayer service was held in Coral Springs. © Getty Images

Scot Peterson, a former sheriff’s deputy who worked as an armed guard at the school, remained outside during the entire shooting. He later resigned in disgrace.

When nothing changed in America after the Sandy Hook Elementary School mass shooting in Connecticut in 2012 – in which 20 children between the ages of six and seven and six staff members were killed – it seemed like it never would. So wedded is the US to its constitutional Second Amendment, even the slaughter of innocent first and second graders was a price worth paying to own a gun with little restriction.

Nothing changed, either, after the worst mass shooting in US history when, last October, 64-year-old Stephen Paddock fired into a crowd of 22,000 concertgoers in Las Vegas from his hotel window, killing 58 and injuring more than 800. Unfathomably, the Las Vegas shooting seemed to drop off the news agenda as quickly as it had arrived.

But something was different with Parkland. Perhaps it was the reaction of the students who survived that made it exceptional, but the wave of gun-control activism they have spearheaded since has been palpable. Eighteen-year-old Emma Gonzalez, with her head shaved and wrist full of friendship bangles, and serious, clean-cut David Hogg, also 18, have unwittingly become the movement’s most recognisable leaders, tirelessly campaigning to address the crisis of gun violence in America.

The morning after Parkland happened, my wife sat in the office at our house in Austin, Texas, emailing the headteacher at our six-year-old’s school, to ask how she planned to keep the students safe. “We agonise about sending our only child into a setting where she can be the victim of gun violence,” she wrote. “It’s heartbreaking and we feel powerless.” She asked about so-called active-shooter drills on campus and what was being done to protect the school.

I’d already been working on this story about mass shootings for a month before Parkland and while my wife was emailing our little girl’s headteacher about gun safety, I was in the other room Facebook messaging with a man, now in his twenties, who, eleven years earlier, had taken his stepfather’s Winchester .270-calibre bolt-action rifle and three boxes of cartridges to his high school, stood in the tall grass in a nearby field and fired into a classroom.

**Las Vegas shooting, 2017, 59 dead, 851 injured ** Stephen Paddock fired more than 1,100 bullets into a crowd of 22,000 people. Investigators found 23 rifles and a handgun in his hotel room. © Shutterstock

Chad Escobedo hadn’t killed anyone that day, and because he was sentenced as a juvenile he had now done his time – a little under six years – and was happily living and working in the Pacific Northwest. I wanted to know what this would-be mass murderer had to say about one of the worst school shootings in US history.

America has the same conversation after each mass shooting, I told him – the inevitable debate about gun control versus mental-health care (rarely both at the same time). It becomes factionalised, politicised and nothing changes. Then the next mass shooting happens. But it occurred to me that the one person we never speak to about mass shootings is the mass shooter himself (and it is, almost always, a him) – perhaps because they too often kill themselves or are dispatched by police. But if we could, we might ask them this: what would have stopped you doing what you did? You tell us. Would it have been some kind of counselling? Would it have been legislation that could have stopped you getting hold of the weapon that caused so much destruction? And what was it that drove you over the edge?

In 2012, researchers at Stanford University began compiling a database listing every mass shooting in America since 1966, creating a single repository for as many reports of mass-shooting events as they could collect online.

Cross-checking, where possible, with individual prison rosters, I found that there were around 50 mass shooters still languishing in prisons across the US. I sent letters to each of them asking them that same question: what could have stopped you doing what you did?

Twelve shooters responded.

The older generation of shooters seem critical of the younger ones

Although the American Medical Association has described gun violence as an epidemic, since 1996 the National Rifle Association, America’s most powerful gun-rights organisation, has striven hard to obliterate this assessment. That’s the year it successfully managed to lobby the Republican-dominated Congress to tack on an amendment (the so-called Dickey Amendment, named after its author, Representative Jay Dickey) to a spending bill that limited funding for any gun-related research by America’s health-protection agency, the Centers For Disease Control And Prevention (CDC).

Troublingly, Mark Rosenberg, the man who was leading the CDC’s studies into gun violence at the time, said he thought the work the organisation was doing could have saved hundreds of thousands of lives. But in the wake of Parkland, for the first time in more than 20 years, Congressional leaders have moved towards lifting the federal ban.

In the interim, though, it’s been up to state governments and private institutions to carry out research. That data has shown that mass shootings are contagious and predictable and that many killers share certain characteristics, such as a history of domestic violence.

In 2013, Congress defined mass killing as three or more murders in a single incident, but definitions of mass shootings differ. The Washington Post, which publishes a mass-shootings tracker, defines it as four or more people killed by a lone shooter. It excludes incidents tied to gang disputes, robberies or those that take place exclusively in private homes. The FBI doesn’t officially define mass shootings, but in the Eighties it established “mass murder” as four or more victims killed in one event in one location. The definition of a mass shooting used for the Stanford database is much broader: three or more shooting victims, not including the shooter himself. It can’t be related to gang violence, drugs or organised crime, but there doesn’t have to be a single fatality.

Including shootings where nobody dies is interesting and I decided to use this definition as well for the following reason: if someone shoots up their school with a bolt-action hunting rifle, injures ten students with glass and shrapnel, but no one dies, does that count as a mass shooting? I think most people would agree that it does. That is, after all, exactly what Chad Escobedo did in April 2007.

I wasn’t trying to kill anybody. I was trying to instil fear. No one cared what I wanted (Chad Escobedo)

Escobedo wasn’t hard to find – and he seemed willing to talk. He was 15 years old when he took his stepfather’s hunting rifle to Springwater Trail High School in Gresham, Oregon.

The school was locked down and surrounding streets closed while police, some with sniffer dogs, swarmed the building. Less than half an hour later, Escobedo was already at his house, confessing to his mum and stepfather. But news reports described anxious parents waiting for news in their parked cars on the other side of the police cordons.

One father received a text message from his son. It read, “Our school was shot with a rifle but I’m OK. I’ll call you when we are out of lockdown.”

Escobedo told police he was angry with two particular teachers and also annoyed with his mother for not letting him live with his biological father. He was inspired by a television documentary on the Columbine High School shootings – the massacre that occurred in 1999 in Colorado, in which two boys killed 12 students and a teacher before taking their own lives. Escobedo’s teachers and fellow students said they were shocked; none could have imagined he would do it.

Of the ten students he injured that day, one required surgery to her neck, while another needed shrapnel and shards of glass removing from her wrist.

When the shooting happened, the photograph the local media used of Escobedo was of a young, fresh-faced, all-American teenager smiling for the camera. Today, on Facebook, little has changed. Now eleven years older, his pictures show him posing in the gym, hiking in the Pacific Northwest, rock climbing and practising archery. His posts reference his love of God, weightlifting (“muscle is my girlfriend”) and football.

Seeing the little green dot appear next to his name in the Facebook Messenger window, I typed: “Looking back, is there anything you think could have been done to stop you doing what you did? Was counselling available? Would you have taken it if it was and do you think it would have helped?”

“I did seek counselling prior to my crime,” he replied. “But the counsellor never took heed [of] what I was talking about, my problems, issues at home, everyday teenage obstacles really.”

I only had access to a gun because I knew where my stepfather kept one (Chad Escobedo)

Escobedo said he may not have gone through with his attack if someone had noticed his behaviour. “What about access to guns?” I asked. “What about legislation to keep guns locked up or improved background checks?”

“I think background checks do enough work,” he said. “Convicted felons can’t access them. Keeping guns from people is never going to happen, especially in the US. The only reason I had access to a gun was because my stepfather owned one and I knew where he kept it.”

Then, Escobedo articulated what I’d been thinking for some time. “If there were a law that said to lock firearms up at home, I think that would’ve prevented me from using his rifle. Children and teens can usually access a firearm if there aren’t any deterrents such as trigger locks or ammunition containers.”

In the UK, where it’s perfectly legal to own rifles and shotguns with a firearms licence, you have to keep them locked up. The gun safe has to be bolted to a wall, the key kept separately and the licence holder should be the only one who knows where it is, otherwise that licence can be revoked. Sure, locking guns up won’t stop all mass shootings – the Las Vegas shooter acquired his arsenal of firearms legally – but it’ll certainly stop some.

We often hear from Second Amendment advocates that if guns weren’t available, the perpetrators of these mass shootings would simply use other weapons, such as knives or homemade bombs. What did Escobedo think?

“There will always be terror in the world,” he wrote. “We can’t hide from that truth. Bad people will come and go and there will be good men to stop them. All sorts of things can be used as a weapon; you can make weapons easily [if you take] the time and effort to figure it out. But disarming a nation will not help at all. I can no longer defend myself when in my own home or out and about downtown. I can’t carry; I’m defenceless. So I sure as hell wouldn’t want any good samaritan next to me to be defenceless as well.”

A few years after he shot up his high school, Escobedo was concerned that he couldn’t own a gun. To someone living in Britain, this may sound absurd. You have to live in America – as I have for the past 15 years – to understand the importance of the Second Amendment to some people. There are in excess of 300 million guns here – more than enough to arm every man, woman and child – so there’s a peculiar logic in thinking that you might feel safer with that many armed people around. (The facts, on the other hand, don’t back that up. Around 30 studies show more guns means more crime. There is far less research demonstrating that guns help.) More disconcerting, perhaps, is hearing that logic from a would-be mass shooter.

Escobedo’s responses seemed dry. A few weeks later, I persuaded him to talk to me on the phone. He was chatty, friendly and it seemed like he genuinely wanted to help. I wanted to understand what drove someone to the brink; what goes through the mind of someone who decides to carry out a mass shooting.

**Sandy Hook, 2012, 28 dead, two injured ** Twenty children aged six to seven and six school staff were killed in Connecticut by 20-year-old Adam Lanza, using a rifle belonging to his mother, who he also killed, as well as himself. © PA Photos

“I think they’re ignored, not listened to,” Escobedo told me one evening. “There are many cases besides mine where mass shootings happened and they found the perpetrator was taking antidepressants or certain drugs. I wasn’t on any drugs. But I wasn’t trying to kill anybody; I was trying to instil fear into the public.”

He came from a good family, he said, and at the time he was living with his mother, stepfather, sister and brother. There was no violence in the household, but he was developing depression and descending into a state where he felt like he wasn’t there, that he didn’t belong.

“I felt trapped, like I was in a cage,” he told me. “I wasn’t liking school. I was never a straight-A student but I didn’t get bad grades. But there was this teacher who was always on my case about certain things. I was texting girls in class and he tried taking my phone away. I called him some names and a feud developed between us. I started failing his classes. I liked soccer but they wouldn’t let me play on the team. It was getting to the point where it was a burden to get up in the morning to go to school. I felt like no one cared what I wanted in life. They thought I was just being an adolescent.”

He remembers a particularly bad argument with his stepfather in which he said he wished he was dead and would go to hell. He went to his bedroom, took a pen and drew a swastika on his left palm. “I’m not a racist, but I knew it was offensive and I did it out of anger. My stepdad found out and started yelling at me, telling me it was the Devil’s sign. One morning shortly after that, I grabbed his gun from the closet. It was a 10lb hunting rifle and packed a lot of power – enough to take down a moose.”

Escobedo said when he stood in the field that day and started shooting into the classroom, he felt an out-of-body experience, as if he was watching himself do it. “In jail, even the counsellor was saying that other people in similar situations said the same thing – that it was like their bodies had taken over. Now I feel, in a way, like I was influenced by something darker.”

Shortly after talking to Escobedo, letters from other mass shooters began arriving in my post-office box.

I was dealing with my own demons and one day in 1992 they got the better of me (Eric Houston)

In 2013, the FBI published a study of the 160 “active shooter incidents” that occurred in America between 2000 and 2013. Its findings made interesting reading. All but two incidents involved a single shooter. In at least nine incidents, the shooter first shot and killed a family member or members at home before moving to a more public location to continue the killing spree. Only six of the shooters were female. And in 40 per cent of cases, the shooters took their own lives. Also, the gunmen in 12 of the 14 high-school shootings that occurred were students at the schools.

Jonathan Metzl, director of the Center For Medicine, Health And Society at Vanderbilt University in Tennessee and an expert on gun violence, told me that, before we can deduce anything from what the mass shooters I’d been in touch with said, you have to consider this: that there have been dramatic changes over the past decades in not only what constitutes a mass shooting, but also the types of weaponry used. “What may have been considered a mass shooting then isn’t now,” he said. “And there is far wider availability of semi-automatic rifles today.”

Metzl said the AR-15 has fundamentally changed what mass shootings look like. The body counts are higher, the acts themselves often far more spectacular. The “copycat phenomenon” has meant mass shooters attempt to outdo each other. The kinds of shootings we saw even in the Nineties barely make the news any more. “Even the recent shooting at a Waffle House in Tennessee [in which four people were killed], we know that within two weeks this will fall out of the news cycle,” he said. “People are desensitised.”

What’s particularly interesting in the interviews that follow, Metzl said, is how critical the older generation of mass shooters seem to be towards the younger generation. It’s a club, he said, of which the older generation don’t seem to want to be a part.

The other thing of note is how articulate some of the killers are. “They’re in prison so they’re probably getting mental-health treatment. Some of the perspective they now have may result from being in a much more structured environment,” he said.

The most interesting thing we can learn from what these shooters tell us, though, is not broad generalisations about mental illness or guns, Metzl said, but is much more about the particulars of the individual cases. “What were the stressors? Why did they do it? The answers to these questions are invaluable. Because many mass shootings result in murder-suicide, we usually don’t get the chance to ask them.”

I was now about to get the opportunity.

The first letter I received was from Silvio Izquierdo-Leyva. In December 1999, Izquierdo-Leyva, a 36-year-old Cuban immigrant who worked as a housekeeper at the Radisson Bay Harbor Inn in Tampa, Florida, burst into the hotel, which was crowded with American football fans, then gunned down four co-workers and shot a fifth person as he was trying to escape. Izquierdo-Leyva was sentenced to life in prison without parole.

**Carthage nursing home shooting, 2009, eight dead, three injured ** Robert Stewart, 45, is believed to have attacked Pinelake Health And Rehabilitation in North Carolina to kill his wife, who worked there. © Shutterstock

He wrote saying he wouldn’t do a face- to-face interview. But his scrawled letter, sent from the Columbia Correctional Institution in Wisconsin, did say that looking back he thought his co-workers could have prevented the attack from happening, that if his behaviour in the workplace had been reported it may not have happened. If guns weren’t available to people with mental problems, Izquierdo-Leyva wrote, mass shootings would be reduced to isolated cases at worst, “since knives would be stoppable and homemade bombs need materials and work, which can be detected before they reach their goal”.

Another letter was from Robert Stewart who, in 2009, aged 45, opened fire at a North Carolina nursing home, killing eight people, and as a result was sentenced to life in prison. He said he didn’t remember the incident as he was on prescription medication at the time, but that all the firearms he possessed were bought legally.

“There’s a serious mental-health issue here in the United States,” he said. “The government keeps dancing around the issue. Their solution is to put mental-health patients in regular prison.”

A few weeks later, Stewart wrote back saying he wanted me to know that he stood behind the Second Amendment. “That’s the only way the people can keep the government from become tyrants,” he said.

One letter was from Eric Houston, who in 1999, aged 20, killed his former teacher and three students with a 12-gauge pump-action shotgun and a sawn-off rifle. It became known as the Lindhurst High School shooting and a California jury sentenced Houston to death. In his letter to me, he said mass shootings happened because of “underlying reasons” such as “depression, anger, isolation, money and family problems”.

He added: “I’ve tried to keep my eye on mass shootings, from Columbine to the Las Vegas shooting that just happened. Animosity, hopelessness and lack of compassion will always be an issue.”

Houston said that he hoped guns would one day be outlawed to the general public and that only a Taser or pepper spray would be available for home defence. “The only people who need guns are the military and state national guard, I think.”

As for his own crime, he wrote that if counselling had been available it may have helped: “But I was dealing with my own demons and one day in 1992 they got the better of me.”

Some letters were short, but still illuminating. Robert Smith carried out a mass shooting in Arizona in 1966, which was believed to be a copycat killing of what’s often cited as the first school shooting in US history. That took place earlier the same year at the University Of Texas at Austin when, after killing his mother and his wife at their homes, Charles Whitman climbed a tower on the university campus and shot and killed 14 people, wounding 31 others, before being shot dead by police. Smith’s copycat shooting in Arizona left five dead and one injured.

If my father’s guns had been locked up... it could have been a different story. You can’t get rid of guns, but put a lock on them at least (William Hardesty)

On a blank postcard, Smith wrote thanking me for my letter, adding, “I strongly suspect your missive represents a mass mailing to mad-dog killers across this country... I wish you good fortune with your enterprise, which sounds most worthwhile. However, I must respectfully decline to participate as my raving lunacy renders my opinions on any subject altogether worthless.”

I wrote back to see if I could change his mind and interview him in person. In an equally short response, he replied: “I can muster no enthusiasm whatsoever for chatting about crimes and criminals or the evil that lurks in the hearts of men. Regarding my own damnable atrocities, I can assure you such would be as distressful for me to relate as for you to hear, if not more so. My advice: leave the Americans behind to merrily murder each other, for clearly such is the fate we were born for.”

Some of the letters contained nothing of substance; others said they couldn’t talk, on instruction from their lawyers. Richard Farley, who in 1988 shot and killed seven people in his workplace and is housed at California’s notorious San Quentin prison, wrote to say, “Years from now, after my appeals are over, I may be interested in giving my opinions on motivations. But not now.”

Andrew Wurst, who was 14 when he killed his science teacher and wounded two students at a middle school dance in Pennsylvania in 1998, wrote to say he couldn’t help with this story “out of respect and consideration for my victims”.

Another, who asked to remain anonymous, wrote that, “One’s will is the true weapon, but I believe that better mental-health services are one of the most obvious and surest ways to have a meaningful impact.”

I didn’t hear back from Jared Loughner, who killed six people and injured Representative Gabby Giffords in Tucson, Arizona in 2010; nor did I get a response from James Holmes, the Aurora, Colorado cinema shooter; or Dylann Roof, the white supremacist who slaughtered nine black people at a Charleston church in 2015.

One mass killer who replied, William Hardesty, agreed to talk to me on the phone from prison. He wrote saying he was high on drugs and alcohol at the time he embarked on a rampage in California and Michigan in 1978, killing seven, and the only thing that might have stopped it “would have been some sleep”.

Arming himself with a pump-action rifle, he shot his father in the back, then waited for his mother to arrive home and shot her in the head while she was washing dishes in the kitchen. He then buried his father’s body under a pile of meat in a freezer that sat on his front porch.

In the early hours of the following morning, he drove to a local bar, Abigail’s Dirty Shame Saloon, and shot two men in the parking lot. A few hours later, he shot and killed his former brother-in-law and wounded another man.

Police arrived at his parents’ house and heard music coming from inside. When they pushed the front door open they heard someone racking a gun. The state troopers took cover behind trees and Hardesty stepped out onto the porch with a rifle. As he pointed it towards them, he was shot in the shoulder and stomach and arrested.

A dramatic black-and-white photograph following his arrest shows Hardesty covered in blood, lying on a stretcher about to be carried into an ambulance, while journalists and TV film crews captured the scene.

An elderly man who lived next door to the Hardesty family told one newspaper that he’d seen Hardesty’s father beating him in the backyard a year before the murders. “His mother had to come out and hit him in the head with a brick to make him stop,” he said.

Instead of trying to talk to my father, I shot him, my mother, my brother-in-law, a guy who worked with him and all the others (William Hardesty)

During his trial, jurors heard Hardesty had embarked on a wild two-day killing spree and that he’d killed because he was “bloodthirsty”. At one early hearing he said he wanted his attorney to “check up on the occult” and asked to be released into the custody of evangelist Billy Graham.

Hardesty’s most recent mugshot shows an old man with grey hair looking solemnly into the camera lens. Since 1981, he’s been known by his Michigan Department Of Corrections number: 163996.

He called me one afternoon from his cell and I asked what would have stopped him doing what he did. “I was doing drugs and going through a divorce,” he said. “I was having nightmares and they got so overwhelming I couldn’t think.”

Hardesty said his father used to hit him on the head repeatedly with a tool from his shed. “I’d get out of work, come over and he’d grab my head. He used to call me ‘Willy Lump Lump’ cos I had so many lumps on my head. But he’s the one who put them there. It just snowballed. I couldn’t handle it. And instead of trying to talk to him – if I did, he’d backhand me – I shot him, my mother, my brother-in-law, a guy who worked with him and the others.”

I asked what he would have done had the weapon – his father’s gun – not been there, if he hadn’t been able to access it. Hardesty said he doubts anyone would have died. “I wouldn’t have got into a fight with him instead. My dad was a big man – a foot taller than me.”

I asked about the Parkland school shooting, the one that was still dominating the news cycle because of a movement that quickly coalesced around surviving students to push legislators to address gun violence in America. “I usually don’t watch the news,” Hardesty said. “My bunkie said somebody shot somebody at school. What are people doing to them to make ’em that way? Kids can be cruel.”

“How do you stop it?” I asked.

“Oh, man. Years ago schools were run by religious people and religion has gone out of schools. Let the church back into schools. They [children] don’t have proper guidance. The week before I shot those people, I was talking to Christian prayer lines, trying to get help. I put myself in a mental hospital three times. I knew I was having problems with my mind, but then I’d get all cleaned up and go drinking again.”

In the US, we have nearly 40,000 gun deaths a year. It’s astronomically higher than all other comparable countries (Jonathan Metzl)

“What about guns?”

“My family all hunted. But if my father’s guns had been locked up... it could have been a different story. You can’t get rid of guns, but put a lock on them at least. If you have guns in your house they have to be locked up unless you are using them. That would stop a lot of people getting killed. You’d be surprised how many people don’t take a drink of alcohol because the cabinet is locked.”

Paul Devoe received a death sentence in Texas for a mass shooting he carried out in 2007. He agreed to an interview with me inside the prison that houses the state’s condemned men.

Marble Falls is a town of about 7,000 people in the picturesque Texas hill country. It was a quiet Sunday evening in August when Devoe, then 43, became enraged after his landlady demanded that he leave her home and he embarked on a killing spree.

Drunk and high on crystal meth, he had fallen asleep with a gun lying next to him (a weapon he borrowed, he’d later insist, to protect against snakes). When he was woken up and turfed out of the house, he said he was consumed by paranoia, grabbed the gun and began shooting at random. Devoe then ran outside to his trailer to get an extra clip and bullets, but when he returned, his landlady had gone. He jumped in a pick-up truck and drove to O’Neill’s Sports Tavern, a regular hangout in Marble Falls. Devoe was dressed in motorcycle clothing, consisting of a black leather vest, jacket, chaps and a cap. It was almost 8pm when he walked in and spotted an ex-girlfriend, Glenda Purcell.

Devoe had badly beaten Purcell two months earlier and she had taken out a protective order against him. Inside the bar, Devoe put his hand over Purcell’s eyes, held a gun to her head and pulled the trigger several times but it didn’t go off. As she ran to the back of the bar, one of the bartenders, Michael Allred, calmly asked Devoe for the gun but Devoe shot him in the chest and ran. Allred died from his wounds.

Devoe then stopped at a petrol station where he bought two 12-packs of Heineken and started drinking. He claims that’s the last thing he remembers.

Here’s what happened next: Devoe then drove to the home of another ex-girlfriend, Paula Griffith, who lived in nearby Jonestown, a tiny town 40 minutes northwest of Austin. When he got there, he shot Griffith, her boyfriend, her 15-year-old daughter and her daughter’s 17-year-old friend. Police discovered the bodies after the 17-year-old’s father became worried when his daughter didn’t call about a planned trip to the Fiesta Texas amusement park.

Devoe then stole a white Saturn station wagon from Griffith’s house and set off on a 1,700-mile drive to New York, where his mother lived. On the way, he called her to confess that he’d just slaughtered five people. As shocking as that must have been to hear, what she didn’t know at that moment was that there would be a sixth.

Hannaford speaks to Paul Devoe behind bulletproof glass, 14 March 2018 © James Breeden

The vehicle Devoe was driving developed stalling problems and was “riding rough”. In Greencastle, Pennsylvania he left Interstate 81 and spotted a car that he liked the look of. He stopped, entered a home, killed an elderly woman and transferred to her Hyundai Elantra. He was eventually arrested at a friend’s house in Long Island after a short standoff with police.

It took a Texas jury just 20 minutes to convict him of the murders in 2009, sentencing him to death. At his trial, jurors were told Devoe began drinking heavily when he was in his early teens and was prone to violent outbursts. He abused a string of women he dated in New York and over the years was in and out of jail. He’d been on death row for almost a decade when he agreed to an interview.

Condemned inmates in Texas are housed at the Allan B Polunsky Unit, a grey fortress in the rural logging town of Livingston. It’s a fairly attractive town, replete with pine trees and a vast lake.

Once through security, I was led into the bowels of the prison and down a sterile corridor to a large room that housed a bank of cells. This is where visitation hours are held. Inmates in general population can sit down face-to-face with their loved ones, but inmates in solitary confinement, such as those on death row, have to conduct visits via telephone from behind bulletproof glass.

Devoe looked much paler than he did in his booking photo a decade ago. He was unshaven, what was left of his hair shorn and he gave me a toothless grin – due, I discovered, to years of crystal meth and alcohol abuse – when I introduced myself. His short-sleeve prison scrubs revealed tattooed paw prints on his right arm (his nickname when he was younger was “Wolf” because he used to work a nightshift at a bakery) and the names of two of his children adorned his other arm and chest.

He told me that when he called his mother after the murders, he also told her that he’d been speaking to his dead grandmother – as if she was still alive.

He said he’d been suffering from depression, had been in and out of hospital having treatment for a snake bite and that the night of the murders he’d drunk a litre of rum and smoked half an ounce of crystal meth.

After I shot up the bar I left there as Satan. If a cop, or Jesus, would have stopped me I’d have killed their ass dead (Luther Casteel)

Devoe was a convicted felon before he embarked on his killing spree and so by law he shouldn’t have been able to access a gun. But he said his work partner was out of town at a wedding and he had a key to his house and knew where he kept his weapon.

I asked what he would have done had he not been able to find the gun. Would he have used a knife instead?

“No,” he said. “If I hadn’t had the gun, it wouldn’t have happened. I wouldn’t have jumped in the truck that night and left.”

Devoe told me his childhood had been rough, that his father was an alcoholic and had beaten him for things his siblings did wrong. Sometimes he’d keep the young Devoe back from school because of the bruises.

“Even to this day, I get panic attacks. I’m on psychotic medication,” he said. “If I hear two guys arguing in here [in prison], I start freaking out. I have a panic attack. I try to turn up my radio, put the headphones on to avoid it, but a lot of the times I can’t. It’s too late. My heart starts racing, I start sweating and I get shaky.”

I asked whether psychotic medication could have changed the outcome ten years ago.

“I believe so,” he said.

“You’re in the unique position,” I told him, “of knowing what came over you the moment you decided to grab that gun and go out and kill six people. Can you describe it, that feeling?” I asked.

“Oh, God,” he said, sighing. “Fear. Loneliness... Yeah. Depressed. It’s hard to explain.”

“But you don’t get those feelings any more?” I asked.

“Yes, I do.”

Luther Casteel, 60, killed two and wounded 16 in a barroom shooting in 2001. He is serving a life sentence at the Menard Correctional Center, Illinois, 4 April 2018 © James Breeden

In many ways there are similarities between what seemed to drive Paul Devoe to the brink and what drove Luther Casteel to kill two people and wound 16 others in a gun rampage in an Illinois bar in 2001. Casteel was sentenced to death a year later, but when George Ryan ended his four-year term as the state’s governor in 2003, he granted clemency to all inmates on death row, claiming the system was unjust. Casteel’s sentence was commuted to life.

The incident for which he’ll eventually die in prison happened in the town of Elgin, northwest of Chicago. Casteel, then 42, had been kicked out of a bar by two bouncers for harassing women, but before he drove home, he vowed revenge. He shaved his head into a mohawk, put on a combat jacket and returned with a .357 magnum in a shoulder holster, a nine-millimetre pistol in a belt and a sawn-off 12-gauge loaded with buckshot.

I went to visit Casteel at the Menard Correctional Center, an hour south of St Louis, Missouri. He’s now housed in general population with other inmates and as such I was able to interview him in person across a metal table. Now 60, Casteel still cuts an imposing figure and during the hour I spent with him, I saw occasional flashes of the temper that he says is the reason he is here.

He told me he has suffered from depression all his life, but wanted to make clear from the outset that he offers no excuse for what he did. “However, I do offer reason,” he said. Casteel claimed he went to a behavioural-health clinic in the late Nineties seeking help, but that the doctor became intimidated by him and ended up calling the police.

There’s no way to verify this, no records to check because no crime was committed. But Casteel still sees this as a catalyst that saw him ultimately spiral out of control. “I have an extremely antisocial personality,” he said. “It’s deep within me, not superficial, where it can be seen, and I have contempt for the police and society in general.”

Casteel was stockpiling weapons and ammunition well before the incident in the bar and was preparing for something “much bigger”, he said. What, exactly, he wouldn’t say, but he would offer this: “I was arming up for an eventual death stand.”

He insisted that the night in question, though, was not premeditated. He didn’t take any guns with him when he went to the pub initially, but he told me that when he was thrown out by bouncers, he felt slighted: “This was the trigger.”

There’s this boy on death row somewhere. It should be his parents (Luther Casteel)

Casteel gritted his teeth and stared into my eyes. After he shot up the bar, he said, he “left there as motherfucking Satan. If a cop would have stopped me, or Jesus, I’d have killed their goddam ass dead.”

Born into a family of – as he puts it – “chronic welfare recipients who were antisocial, anti-education and didn’t give a damn about us kids”, Casteel grew up with his two brothers on the streets of Chicago. His first arrest came at the age of 12 and he was in and out of juvenile institutions for most of his teenage years. There, associating with older criminals, enabled him to “learn the game”. Even today in Menard, he is incarcerated with men he has known since he was 13.

He has read about other mass shootings over the years. One in particular, he said, made him particularly sad, when the then 21-year-old white supremacist Dylann Roof shot and killed nine black worshippers at the Emanuel African Methodist Episcopal Church in Charleston, South Carolina in 2015 – including the senior pastor and state senator Clementa C Pinckney.

“Somebody poisoned that kid to make him hate people like that cos it’s just not a natural thing to hate people because of their colour,” he said. “And there’s this boy who now sits on death row in a federal penitentiary somewhere [when in fact] they should have his mother and father on death row.”

For Casteel, it’s very much about nurture, not nature. Mass killers are not prewired. So what about Casteel’s own parents? Did he think they were culpable?

“They should have been hanged,” he said. “The prison authorities came to me in 2005 when I was in state penitentiary to tell me my dad had died. You may as well have told me it was raining outside because it made no difference to me whatsoever.”

Casteel said his parents poisoned him and his two brothers. He was 13 years old when he first shot a gun. He’d steal to get money to eat and would sleep under porches, on rooftops, in garages and when he started finding guns in the houses he had robbed, he began using them to carry out armed robberies too.

GQ’s Alex Hannaford spoke to Luther Casteel at the Menard Correctional Center, Illinois, where he has been imprisoned since 2002, 4 April 2018 © James Breeden

So what about guns, I asked. Would he have committed the crimes for which he’s now serving a life sentence if he hadn’t been able to access them?

“I hear a lot about gun control and truly it’s laughable,” he said. “You will never ever rid the United States Of America of guns. Guns are all over the street. Did I have to get a background check to get an eight-ball of cocaine? No. All I had to have was a little money. There’s so many guns in this country it’s just pathetic. It’s asinine.”

Jonathan Metzl, the gun violence expert I’d spoken to at Vanderbilt University, said it’s a fantasy to think that a single pill or a specific psychiatric treatment could stop somebody committing a mass shooting. And mass shootings can’t be solved by only addressing mental illness or guns. “It’s multi-factorial,” he said.

“In the US, we have nearly 40,000 gun deaths a year. It’s astronomically higher than all other comparable countries. It’s frustrating when people say, ‘There is no one law that would reduce gun deaths so let’s do nothing.’ You can have safe storage practices. You can have universal background checks and close the loopholes. It’s not a mystery what we need to do to reduce gun deaths, but we are up against the headwind of a very powerful corporate gun lobby.”

Mass shootings are hard to predict but one thing that could help is if we can identify somebody spiralling out of control, like most of the mass shooters I’ve spoken to. The Gun Violence Restraining Order is a piece of legislation designed to address just that. “People who are at risk can alert authorities if they feel their husband, father or boyfriend is escalating, spiralling out of control,” Metzl said. “And they can take away their guns before they can do harm.”

If you can imagine you’re about to be attacked or about to attack, your adrenalin is so powerful it’s got your hands and face shaking (Luther Casteel)

Since Parkland, the number of states that give courts the power to intervene and disarm people showing warning signs of violence or in the throes of a crisis has doubled. In most states, a person must be convicted of a crime before they lose their right to have a firearm. But so-called red flag gun bills are gaining in popularity. Before Valentine’s Day this year, only Connecticut, California, Washington, Oregon and Indiana had red flag laws. Now, Florida, Vermont, Rhode Island, New Jersey, Delaware and Maryland have joined them, with Illinois and Texas looking set to follow.

Our daughter now sleeps on a mattress on our bedroom floor, too afraid to be in her own room at night. Since Parkland, she’s the one who puts the burglar alarm on at night. So what do we do? Move to a state with less gun violence or one that is taking it seriously, with red flag laws and gun restrictions? Or leave the US for good?

Perhaps, in some small way, it’s comforting to note that many of the mass shooters I interviewed or corresponded with indicated that there were warning signs before they embarked on their rampages, that their decision to kill didn’t happen in a vacuum. Perhaps, in addition to making it harder to get hold of weapons, we need to get better at spotting the signs.

Age may have tempered slightly the rage Luther Casteel felt in 2001, but he told me he still feels it now, after a decade and a half in prison, even though he can no longer drink alcohol and is able to take out some of that aggression on the weight bench.

I asked him what triggered it. “Anything,” he said, and when it happens, his adrenalin rockets. I wanted to know what that felt like. “If you can imagine you’re about to be attacked or about to attack, your adrenalin is so powerful it’s got your hands and face shaking,” he said. “It leaves you drained if you don’t do anything about it.”

The question is, how do we stop future Luther Casteels from acting on that rage? I believe it comes back to those warning signs. If they (or someone they know) can spot them, they can get help to temper it.

**Orlando nightclub shooting, 2016, 49 dead, 53 wounded ** Omar Mateen’s attack on a gay clubnight resulted in 49 deaths. At the time it was America’s deadliest strike by a lone gunman. © Getty Images

Certain psychotic events can be treated with medication and/or therapy. Each state has a law allowing police to take someone to a mental-health emergency room if necessary for evaluation. Then they’re either sectioned or they’re sent home. If it’s the latter, what’s the next step?

According to one mental-health expert I spoke to, there rarely is one. But if there was a sponsor designated by the state to ensure that a person couldn’t access weapons and continued to see a doctor on a regular basis – and that if they didn’t and they were worried they could recommend they be detained – that seems like a good idea. As one psychiatrist told me, “We are lacking this third party.”

The government needs to make that help available, which is why solutions to gun violence are bound up with the healthcare debate. Healthcare is expensive in America, but treatment for would-be killers needs to be free. Those without health insurance could qualify for government help through the Medicaid or Medicare programmes, but sometimes red tape is enough to stop someone getting help.

With that help, though, perhaps Nikolas Cruz would have never opted to use a weapon of war in that three-storey Parkland school building in February earlier this year, and perhaps Stephen Paddock would never have fired more than 1,100 rounds from his room on the 32nd floor of the Mandalay Bay hotel into a crowd of concertgoers in October 2017.

Red flag laws may enable authorities to remove weapons from those at risk, but at the moment it’s too early to tell whether it’s affecting murder rates. What we know is that they’re primarily being enforced to prevent suicide. According to a study by the University Of Indianapolis, in some years as much as 80 per cent of all gun confiscations in Indiana have been because of concern over the risk of suicide rather than murder and it is said to correlate with a 7.5 per cent drop in people taking their own life with a gun. Weapons seizures are clearly having an impact.

But guns are the elephant in the room. There needs to be a federal law that makes locking up weapons mandatory. If there had been such a law, Paul Devoe may never have been able to access his friend’s gun in Marble Falls eleven years ago. And perhaps Chad Escobedo would never have taken his stepfather’s Winchester rifle to his Oregon school that morning in 2007.

None of this will stop all gun violence in the US, but it will reduce it – possibly to a fraction of what it is at the moment. Right now, it’s an epidemic. The good news is that momentum for change seems to be building, but only when real change comes will we all sleep a little easier.

**Read more: **

What the US can learn from UK gun control

Why the US won't give up its guns

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