The teen entered the chat with a friendly greeting.

“Hello lads,” he typed.

“Sup,” came a reply, along with a graphic that read “KILL JEWS.” Another poster shared a GIF of Adolf Hitler shaking hands with Benito Mussolini. Someone else added a short video of a gay pride flag being set on fire. Eventually, the talk in the group turned to mass shootings and bombings.

And so in August 2019, Juraj Krajčík, then a soft-faced 16-year-old with a dense pile of brown hair, immersed himself in a loose collection of extremist chat groups and channels on the massive social media and messaging platform Telegram. This online community, which was dubbed Terrorgram, had a singular focus: inciting acts of white supremacist terrorism.

Over the next three years, Krajčík made hundreds — possibly thousands — of posts in Terrorgram chats and channels, where a handful of influential content creators steered the conversation toward violence. Day after day, post after post, these influencers cultivated Krajčík, who lived with his family in a comfortable apartment in Bratislava, the capital of Slovakia. They reinforced his hatreds, fine-tuned his beliefs and fed him tips, encouraging him to attack gay and Jewish people and political leaders and become, in their parlance, a “saint.”

On Oct. 12, 2022, Krajčík, armed with his father’s .45-caliber handgun, opened fire on three people sitting outside an LGBTQ+ bar in Bratislava, killing two and wounding the third before fleeing the scene.

That night, as police hunted for him, Krajčík spoke on the phone with Marek Madro, a Bratislava psychologist who runs a suicide hotline and mental health crisis team. “He hoped that what he had done would shake up society,” recalled Madro in an interview, adding that the teen was “very scared.”

During the call, Krajčík kept repeating phrases from his manifesto, according to Madro. The 65-page document, written in crisp English and illustrated with graphics and photos, offered a detailed justification for his lethal actions. “Destroy the degenerates!” he wrote, before encouraging people to attack pride parades, gay and lesbian activists, and LGBTQ+ bars.

Eventually Krajčík, standing in a small grove of trees alongside a busy roadway, put a gun to his head and pulled the trigger.

The next day, Terrorgram influencers were praising the killer and circulating a PDF of his manifesto on Telegram.

“We thank him from the bottom of our hearts and will never forget his sacrifice,” stated one post written by a Terrorgram leader in California. “FUCKING HAIL, BROTHER!!!”

The story of Krajčík’s march to violence shows the murderous reach of the online extremists, who operated outside the view of local law enforcement. To police at the time, the killings seemed like the act of a lone gunman rather than what they were: the culmination of a coordinated recruiting effort that spanned two continents.

ProPublica and the PBS series FRONTLINE, along with the Slovakian newsroom Investigative Center of Jan Kuciak, pieced together the story behind Krajčík’s evolution from a troubled teenager to mass shooter. We identified his user name on Telegram, which allowed us to sift through tens of thousands of now-deleted Telegram posts that had not previously been linked to him. Our team retraced his final hours, interviewing investigators, experts and victims in Slovakia, and mapped the links between Krajčík and the extremists in Europe and the U.S. who helped to shape him.

The Terrorgram network has been gutted in recent months by the arrests of its leaders in North America and Europe. Telegram declined repeated requests to make its executives available for interviews but in a statement said, “Calls for violence from any group are not tolerated on our platform.” The company also said that since 2023 it has stepped up moderation practices.

Still, at a time when other mainstream social media companies such as X and Meta are cutting back on policing their online content, experts say the violent neo-Nazis that populated Telegram’s chats and channels will likely find an online home elsewhere.

At first, Krajčík didn’t fit in with the Terrorgrammers. In one early post in 2019, he argued that the white nationalist movement would benefit from large public protests. The idea wasn’t well received.

“Rallies won’t do shit,” replied one poster.

Another told the teen that instead of organizing a rally, he should start murdering politicians, journalists and drag performers. “You need a mafia state of mind,” the person wrote.

Krajčík had found his way to the Terrorgram community after hanging out on 8chan, a massive and anonymous forum that had long been an online haven for extremists; he would later say that he was “redpilled” — or radicalized — on the site.

On 8chan, people posted racist memes and made plenty of vile comments. But the Terrorgram scene was different. In the Terrorgram chats people discussed, in detail, the best strategies for carrying out spectacular acts of violence aimed at toppling Western democracies and replacing them with all-white ethno-states.

The chats Krajčík joined that summer of 2019 were administered by Pavol Beňadik, then a 20-year-old Slovakian college student who had helped create the Terrorgram community and was one of its leading personalities.

A hybrid of a messaging service like WhatsApp and a social media platform like X or Facebook, Telegram offered features that appealed to extremists like Beňadik. They could engage in private encrypted discussions, start big chat groups or create public channels to broadcast their messages. Importantly, Telegram also allowed them to post huge PDF documents and lengthy video files.

In his Terrorgram chats, Beňadik, who used the handle Slovakbro, relentlessly pressed for violent actions — although he never took any himself. Over two days in August, he posted instructions for making Molotov cocktails and pipe bombs, encouraged people to build radioactive dirty bombs and set them off in major cities, and called for the execution of police officers and other law enforcement agents. “TOTAL PIG DEATH,” he wrote.

At the time, the chats were drawing hundreds of participants from around the world, including a large number of Americans.

Beňadik, who was from a small village in western Slovakia, took a special interest in Krajčík, chatting with him in the Slovak language, discussing life in their country, and making him feel appreciated and respected.

For Krajčík, this was a change. In his daily life outside of Terrorgram, he “felt completely unnoticed, unheard,” said Madro, who spoke with several of Krajčík’s classmates. “He often talked about his own feelings and thoughts publicly and felt like no one took him seriously.”

Krajčík started spending massive amounts of time in the chat. On a single day, he posted 117 times over the span of 10 hours. The teen’s ideas began to closely echo those of Beňadik.

In late September, two regulars had a friendly mixed martial arts bout and streamed it on YouTube. Krajčík shared the link with the rest of the chat group, who cheered and heckled as their online friends brawled. Beňadik encouraged Krajčík to participate in a similar bout in the future.

“Porozmýšlam,” replied Krajčík: “I’ll think about it.”

For Beňadik, the combatants were providing a good example. He wanted Terrorgrammers to transform themselves into Aryan warriors, hard men capable of doing serious physical harm to others.

In reality, Krajčík was anything but a tough guy. A “severely bullied student,” Krajčík had transferred to a high school for academically gifted students, a school official told the Slovak newspaper Pravda. Two therapists “worked intensively with him for two years until the pandemic broke out and schools closed,” the official said.

Beňadik created at least five neo-Nazi channels and two chat groups on Telegram, one of which eventually attracted nearly 5,000 subscribers. He crafted an online persona as a sage leader, offering tips and guidance for carrying out effective attacks. He often posted practical materials, such as files for 3D-printing rifle parts, including auto sears, which transform a semiautomatic gun into a fully automatic weapon. “Read useful literature, get useful skills,” he said in an interview with a podcast. “You are the revolutionary, so act like it.”

It was only a month after joining Beňadik’s Terrorgram chats that Krajčík first mentioned Tepláreň, the LGBTQ+ bar in Bratislava he eventually attacked. On Sept. 18, 2019, he shared a link to a website called Queer Slovakia that featured an article on the bar.

Beňadik responded immediately, writing that he was having a “copeland moment” — a reference to David Copeland, a British neo-Nazi who planted a nail bomb at an LGBTQ+ pub in London in 1999. The explosion killed three people and wounded nearly 80 others.

“I DON’T ACTUALLY WANT TO NAIL BOMB THAT JOINT,” Beňadik continued. He wanted to do something far worse. “Hell,” Beňadik wrote, would be less brutal than what he had in mind.

Another Terrorgrammer offered a suggestion: What about a bomb loaded with “Nails + ricin + chemicals?”

Krajčík sounded a note of caution. “Just saying it will instantly make a squad of federal agents appear behind you and arrest you,” he wrote. Beňadik responded by complaining that Slovakia wasn’t producing enough “saints,” implicitly encouraging his mentee to achieve sainthood by committing a lethal act of terror.

Two days later, Krajčík posted photos of people holding gay pride flags in downtown Bratislava. They were “degenerates,” he wrote, repeatedly using anti-gay slurs.

One chat member told Krajčík he should’ve rounded up a group of Nazi skinheads and assaulted the demonstrators.

Then Krajčík posted a photo of Tepláreň.

Beňadik responded that “airborne paving stones make great gifts for such businesses.”

In the chat, Beňadik repeatedly posted a PDF copy of the self-published memoirs of Eric Rudolph, the American terrorist who bombed the 1996 Olympic Games in Atlanta and several other sites before going on the run. The autobiography contains a detailed description of Rudolph’s bombing of a lesbian bar, which wounded five people.

Urging Krajčík to read the book, Beňadik described it as “AMAZING” and a “great read.” Rudolph, he wrote, had created the “archetype” for the “lone wolf” terrorist.

Eventually, Krajčík joined at least 49 extremist Telegram chats, many of them nodes in the Terrorgram network, according to analysis by Pierre Vaux, a researcher who investigates threats to democracy and human rights abuses.

While Terrorgram started as a loose collection of accounts, by 2021 Beňadik and some of his fellow influencers had created a more formal organization, which they called the Terrorgram Collective, according to interviews with experts and court records from Slovakia, the U.S. and Canada.

The organization began producing more sophisticated content — books, videos and a roster of potential assassination targets — and distributing the material to thousands of followers.

Krajčík was a fan of the collective’s books, which are loaded with highly pixelated black-and-white graphics and offer a raft of specific advice for anyone planning a terror attack.

By the summer of 2022, Krajčík had become a regular poster in a Terrorgram chat run by another alleged leader of the collective, Dallas Humber of Elk Grove, California, a quiet suburb of Sacramento.

Humber went by a series of usernames but was eventually publicly exposed by a group of activists, and later arrested and charged with terrorism-related offenses. ProPublica and FRONTLINE reviewed chat logs — provided by the anti-facist Australian research organization The White Rose Society — and other online materials, as well as court records, to independently confirm her identity.

Beňadik was arrested in Slovakia and charged with more than 200 terrorism offenses. He pleaded guilty and would be sentenced to six years in prison.

In his absence, Humber quickly slipped in as mentor and coach to Krajčík.

She was explicit about her intentions, constantly encouraging followers in her chats and channels to go out and kill their perceived enemies — including Jewish and Muslim people, members of the queer community and anybody who wasn’t white. Her job, she wrote in one post, was to embrace disaffected young white men and guide them “through the end of the radicalization process.”

On Aug. 2, 2022, Humber and Krajčík discussed a grisly incident that had occurred several days earlier: A white man had beaten to death a Nigerian immigrant on a city street in northern Italy.

The killing, which was documented on video, was “fucking glorious,” wrote Humber, using a racial slur to describe the victim. “Please send any more pics, articles, info to the chat as more details come out,” she posted.

Krajčík wrote that he didn’t know much about the circumstances surrounding the crime but was still convinced the murderer had chosen “the right path.”

The killer, wrote Humber, would make an “ideal” boyfriend. “Every girl wants a man who would kill a [racial expletive] for her 🥰 how romantic.”

Three days later, Humber’s chat was alive with tributes to and praise for another killer. Wade Page, a Nazi skinhead and former U.S. Army soldier, had murdered six Sikh worshippers at a temple outside of Milwaukee a decade earlier. (A seventh would later die of their injuries.)

When police confronted Page, he began shooting at them, hitting one officer 15 times before killing himself.

Humber was a big fan of the killer. Page, she wrote, planned the attack thoroughly and chose his targets carefully. “He even made a point to desocialize and cut ties with those close to him,” Humber noted. “No chance of them disrupting his plans.”

“Page did his duty,” Krajčík wrote.

During the same time period, Krajčík started doing reconnaissance on potential targets in his city, staking out the apartment of then-Prime Minister Eduard Heger, a Jewish community center and Tepláreň, the bar.

He posted photos of the locations on his private Twitter account. And in a series of cryptic tweets, Krajčík hinted at the violence to come:

“I don’t expect to make it. In all likelyhood I will die in the course of the operation.”

“Before an operation, you will have to mentally deal with several important questions. You will have to deal with them alone, to not jeopardize your mission by leaking it.”

“I want to damage the System to the best of my abilities.”

Then, on Oct. 11, 2022, he wrote:

“I have made my decision.”

The next evening, after spending a half-hour outside the prime minister’s apartment, Krajčík made his way to Tepláreň. The bar sat on a steep, winding street lined with cafes, clothing boutiques and other small businesses. For about 40 minutes he lurked in a shadowy doorway up the hill. Then, at about 7 p.m., he approached a small group of people sitting in front of the bar and began shooting.

He killed Matúš Horváth and Juraj Vankulič and wounded Radka Trokšiarová, shooting her twice in the leg.

Krajčík, then 19, fled the scene. He had just committed a terrorist attack that would shock the nation.

In court records, U.S. prosecutors have linked both Humber and another alleged Terrorgram leader, Matthew Allison of Boise, Idaho, to Krajčík’s crime. The pair were charged last fall with a raft of felonies related to their Terrorgram posts and propaganda, including conspiring to provide material support to terrorists and soliciting the murder of federal officials.

Krajčík “was active on Terrorgram and had frequent conversations with ALLISON, HUMBER, and other members of the Terrorgram Collective,” prosecutors allege in the indictment. In another brief, they say Krajčík shared his manifesto with Allison before the attack. Then, immediately after the murders, he allegedly sent Allison direct messages saying, “not sure how much time I have but it’s happening,” and “just delete all messages about this convo.”

The Terrorgram posts cited in court documents corroborate our team’s reporting.

Allison spoke with one of our reporters from jail against his lawyer’s advice. He said he did not incite anyone to violence and that prosecutors had misconstrued the communications with Krajčík. He has pleaded not guilty to all charges, and in a motion, his legal team indicated it would argue that all of his posts are protected by the First Amendment. Humber also pleaded not guilty. She declined to be interviewed and to comment through her lawyer.

While Krajčík was at large, Slovakian authorities tapped Madro, the psychologist, to try to communicate with the young man. “After 12 text messages, he finally picked up the phone,” Madro recalled.

The brief conversation ended with Krajčík killing himself. “The shot rang out and there was silence,” Madro said.

Within hours, Humber was making celebratory posts. Krajčík, she exclaimed, had achieved sainthood. “Saint Krajčík’s place in the Pantheon is undisputed, as is our enthusiastic support for his work,” she wrote on a Terrorgram channel where she posted a picture of the victims on the ground, blood streaking the pavement.

She and Allison also circulated his manifesto.

In it, Krajčík praised the Terrorgram Collective for its “incredible writing and art,” “political texts” and “practical guides.” And he thanked Beňadik: “Your work was some of the first that I encountered after making the switch to Telegram, and remains some of the greatest on the platform.”

While they were spreading Krajčík’s propaganda, the owner of Tepláreň, Roman Samotný, was mourning.

The bar “was kind of like a safe island for queer people here in Slovakia,” he recalled in an interview. “It was just the place where everybody felt welcomed and just accepted and relaxed.”

Before the attack, Samotný’s major concern was that some homophobe would smash the bar’s windows. After the murders, he said, “the biggest change is the realization that we are not anymore safe here. … I was never thinking that we can be killed because of our identity.”

Samotný has closed the bar.

The survivor, Trokšiarová, was left with lingering physical pain and emotional distress. “I was deeply confused,” she said. “Why would anyone do it?”