by A.C. Thompson, ProPublica and FRONTLINE, and James Bandler, ProPublica

This story contains references to homophobia, antisemitism and racism, as well as mass shootings and other violence.

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On Jan. 19, 2024, the sheriff of Jacksonville, Florida, released a 27-page manifesto left behind by Ryan Palmeter, a 21-year old white man who had murdered three Black people at a Dollar General store before turning the gun on himself.

The Florida Times-Union, a prominent local news outlet, said it would not be publishing the document, which it said used the N-word 183 times and had an “overall theme of white superiority.” T.K. Waters, the sheriff, said he had posted what he described as the “rantings of an isolated, hateful, madman” to keep his promise of public transparency. An attorney for one of the victims’ families urged the public “to not give Palmeter the satisfaction of publishing or distributing his manifesto,” saying it “contains not one redeemable thought.”

Thousands of miles away, in Elk Grove, California, Dallas Humber saw Palmeter’s view of the world as perfect for her audience of online neo-Nazis. Humber, a now-35-year-old woman with a penchant for dyeing her hair neon colors, was a leading voice in an online network of white supremacists who had coalesced in a dark corner of Telegram, a social media and messaging service with almost a billion users worldwide.

She and her comrades called this constellation of interlocking Telegram accounts Terrorgram. Their shared goal was to topple modern democracies through terrorism and sabotage and then replace them with all-white ethno-states.

Humber quickly turned Palmeter’s slur-riddled manifesto into an audiobook that she narrated in a monotone. Then she sent it into the world with her signature line:

“So, let’s get this party started, Terrorbros.”

The manifesto immediately began to spread, pinballing around the worldwide Terrorgram scene, which celebrated mass shooters like Palmeter as “saints.”

The Terrorgram story is part of a much larger 21st century phenomenon. Over the past two decades, massive social networks like X, Facebook and Telegram have emerged as a powerful force for both good and evil. The ability to connect with like-minded strangers helped fuel uprisings like the Arab Spring and Iran’s pro-democracy movements. But it has also aided extremists, including brutal jihadist organizations like the Islamic State group and white supremacists around the world.

This story is part of a collaborative investigation from FRONTLINE and ProPublica that includes an upcoming documentary, “The Rise and Fall of Terrorgram,” which premieres March 25 at 10 p.m. EDT/9 p.m. CDT on PBS stations (check local listings) and will be available to stream on YouTube, the PBS App and FRONTLINE’s website.

Telegram, which is massively popular outside of the U.S., boasted an array of features that appealed to Humber and her fellow Terrorgammers. They could send encrypted direct messages, start big chat groups and create public channels to broadcast their messages. In the span of five years, they grew Terrorgram from a handful of accounts into a community with hundreds of chats and channels focused on recruiting would-be terrorists, sharing grisly videos and trading expertise on everything from assassination techniques to the best ways to sabotage water systems and electrical transmission lines. On one of her many accounts, Humber posted step-by-step instructions for making pipe bombs and synthesizing HMTD, a potent explosive.

Humber went by a series of usernames but was eventually publicly exposed by a group of California activists. ProPublica and FRONTLINE reviewed chat logs — some provided by the Australian anti-facist research organization The White Rose Society — court records and Humber’s other digital accounts to independently confirm her identity.

U.S. prosecutors say Humber helped lead the Terrorgram Collective, a transnational organization that ran popular Terrorgram accounts, produced sophisticated works of propaganda and distributed an alleged hit list of potential assassination targets. She is currently facing a host of federal terrorism charges, along with another alleged Terrorgram leader, Matthew Allison, a 38-year-old DJ from Boise, Idaho. Both have pleaded not guilty.

To trace the rise and fall of Terrorgram, ProPublica and FRONTLINE obtained a trove of chat logs and got access to some of the extremists’ private channels, allowing reporters to track in real time their posts and relationships. We combed through legal documents, talked with law enforcement officials and researchers in six countries and interviewed a member of the collective in jail. Taken together, our reporting reveals new details about the Terrorgram Collective, showing how Humber and her compatriots were powerful social media influencers who, rather than peddling fashion or food, promoted murder and destruction.

The material illustrates the tension faced by every online platform: What limits should be imposed on the things users post or discuss? For years, social networks like Facebook and X employed thousands of people to review and take down offensive content, from pornography to racist memes to direct incitement of violence. The efforts at content moderation prompted complaints, primarily from conservatives, that the platforms were censoring conservative views of the world.

Telegram was created in 2013 by Pavel Durov, a Russian-born technologist, and his brother Nikolai. Pavel Durov, a billionaire who posts pictures of himself on Instagram, baring his chiseled torso amid rock formations and sand dunes, became the face of the company. He marketed the platform as a free-speech-focused alternative to the Silicon Valley social media platforms, which in the mid-2010s had begun aggressively policing disinformation and racist and dehumanizing content. Telegram’s restrictions were far more lax than those of its competitors, and it quickly became a hub for hate as well as illegal activity like child sexual exploitation and gunrunning.

Our review of thousands of Terrorgram posts shows that the lack of content moderation was crucial to the spread of the collective’s violent content. Telegram’s largely hands-off approach allowed Humber and her alleged confederates to reach an international audience of disaffected young people.

They encouraged these followers to turn their violent thoughts into action. And some of them did.

ProPublica and FRONTLINE identified 35 crimes linked to Terrorgram, including bomb plots, stabbings and shootings. Each case involved an individual who posted in Terrorgram chats, followed Terrorgram accounts or was a member of an organized group whose leaders participated in the Terrorgram community.

One of the crimes was a 2022 shooting at an LGBTQ bar in Bratislava, Slovakia, that left two people dead and another injured. In an earlier story, ProPublica and FRONTLINE detailed how the shooter, Juraj Krajčík, was coached to kill over three years by members of the Terrorgram Collective, a process that started when he was just 16 years old.

Radka Trokšiarová survived the Bratislava attack after being shot twice in the leg. “Sometimes I catch myself wishing to be able to ask the gunman: ‘Why did you do it? What was the........

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