About 35 minutes was broadcast live on Twitch in latest instance of extremists using shootings to promote propaganda

The suspected gunman in the Yom Kippur synagogue attack in Halle, Germany, broadcast his rampage on the livestreaming platform Twitch, in the latest instance of rightwing extremists using mass shootings to create and promote real-time propaganda.

About 35 minutes of video was broadcast live on Twitch, an Amazon-owned platform that is primarily used by video game players, the company confirmed on Wednesday. Twitch removed the video but copies had already been downloaded and shared elsewhere on the internet, highlighting the challenges faced by platforms attempting to stymie the dissemination of such material.

Having failed to enter the synagogue by shooting at the locks, the gunman shot dead two people nearby. Two others were injured. He was arrested after fleeing the scene.

The Halle attack is the second livestreamed rightwing extremist attack this year, following the March massacre of 51 Muslim worshippers in Christchurch, New Zealand, which was broadcast on Facebook Live. The alleged gunman in the April synagogue shooting in Poway, California, shared a Facebook Live link in a manifesto posted on the extremist message board 8chan before his attack, suggesting that he planned to livestream the shooting that left one dead and two injured.

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“Livestreaming enables extremists to amplify their actions, but even more so, bringing their supporters and others that they want to inspire on the journey with them,” said Oren Segal, director of the Anti-Defamation League’s Center on Extremism. “It is an interactive radicalization tool that also helps spread content that may inspire the next attacker after them.”

Aspects of the video, which was reviewed by the Guardian, appear designed for this exact purpose. The video opens with the suspect introducing himself in English to the camera as “Anon” and declaring himself an antisemite, anti-feminist and Holocaust denier. The use of English suggests he had an international audience in mind, and a reference to falling birth rates is in line with popular white nationalist tropes. “Anon” is internet lingo for an anonymous user of forums such as 4chan and 8chan.

“These folks are preparing their social media strategy as they prepare their weapons,” Segal said. “That’s the modern terrorist.”

The Halle shooter also appears to have emulated the Christchurch and Poway shooters by preparing a “manifesto” and posting it online before his attack. Three documents describing the motivation and weaponry for the attack were posted on the imageboard site meguca.org, according to the International Centre for the Study of Radicalisation at King’s College London.

The documents, which include a link to the livestream of the shooting, are vehemently antisemitic and racist. They state that the attack’s timing – on Yom Kippur, the Jewish day of atonement and one of the religion’s high holidays – was intentional. They also assert the shooter considered a mosque or “antifa ‘culture’ center” as alternate targets.

“We worked with urgency to remove this content and will permanently suspend any accounts found to be posting or reposting content of this abhorrent act,” said Brielle Villablanca, a spokeswoman for Twitch.

The video was viewed by just five people during the attack, the company said, and by about 2,200 people in the 30 minutes after the attack had ended and before Twitch took it down.

“This video was not surfaced in any recommendations or directories,” the company said in a statement posted on Twitter. “Instead, our investigation suggests that people were coordinating and sharing the video via other online messaging services.”

Despite this limited initial audience, however, the video has since been broadly disseminated on Telegram, an encrypted messaging app that has become a haven for white nationalists and other far-right extremists. One copy of the video had been viewed by more than 33,000 people on Telegram as of Wednesday afternoon. Edited versions of the video were also being shared openly on Twitter throughout the day on Wednesday.

Twitch said that it had shared the video’s hash – a unique fingerprint for a photo and video that can be used to detect it automatically – with an industry consortium to help prevent the spread of the video onto other platforms. A spokesperson for Facebook confirmed that the company was working to remove and block the video from its platforms. YouTube and Twitter did not immediately respond to queries.

“We’re having the same conversation every few months, and it’s just going to different platforms,” Segal noted. “Instead of talking about 8chan, today it’s Telegram. Instead of a Facebook stream, we’re talking about Twitch. I think that underscores a broader issue that extremists will migrate from platform to platform.”

Becca Lewis, a research affiliate at Data & Society who studies online political subcultures, agreed that there are no simply technical solutions, though tech companies should work to limit the reach of such videos.

“We’re past the point where it would make sense to simply disable livestream for platforms like YouTube, Facebook and Twitch – there are entire economies built around them by now,” she said. “So I think we need to be thinking about preventative measures that more broadly tackle racism and bigotry in society, which is of course a long and grueling process.”

Philip Oltermann contributed reporting