A new, nearly 800-page report on the 2019 Christchurch shooting claims that mainstream social media platforms had a much larger role in radicalizing the shooter than fringe websites.

The two platforms that had the biggest impact on the shooter’s mindset: YouTube and Facebook.

Following the attack that left 51 people dead at two Christchurch mosques in March of last year, the New Zealand government launched an independent inquiry into the spree killing. The results of that report paint a picture of how the shooter, white supremacist Brenton Tarrant, came to commit such a heinous act.

The report specifically found that YouTube played a major role in radicalizing the man.

“What particularly stood out was the statement that the terrorist made that he was ‘not a frequent commentator on extreme right-wing sites and YouTube was a significant source of information and inspiration’,” said New Zealand Prime Minister Jacinda Ardern while discussing the report. “This is a point I plan to make directly to the leadership of YouTube.”

Tarrant was a fan of the once-prominent far-right YouTuber Stefan Molyneux, as well as other figures on the right such as white nationalists Richard Spencer and Lauren Southern. According to the report, Tarrant even donated money to right-wing organizations and Freedomain Radio, which was created by Molyneux. YouTube banned both Molyneux and Spencer from the platform this past summer. 

“We’ve made significant progress in our work to combat hate speech on YouTube since the tragic attack at Christchurch,” said a YouTube spokesperson in an email. “In 2019 we strengthened our hate speech policy which has resulted in the termination of channels mentioned in the report, and led to a 5x spike in the number of hate videos removed from YouTube.” 

YouTube also said it made changes to its recommendation algorithm in order to limit the spread of similar video content that doesn’t quite cross the line and violate the platform’s policies.

“We will continue our work together with the Prime Minister, as well as governments, industry partners, and communities around the world to combat the spread of violent extremism online,” the spokesperson continued.

Facebook also played a role in the radicalization of the Christchurch shooter, according to the report.

Tarrant frequently posted Islamophobic rhetoric in far-right Facebook Groups such as The Lads Society Season Two, United Patriots Front, and True Blue Crew. He also spoke about inspiration he pulled from Adolf Hitler’s Mein Kampf on the social network.

In one particularly interesting exchange, pointed out by Vice, Tarrant’s mother calls him a “neo-Nazi” in a Facebook message. Tarrant was bothered by this because he worried Facebook’s moderation systems would detect the word and take action against his account.

Mashable reached out to Facebook for comment and will update this piece when we hear back.

Many social media platforms grappled with issues stemming from the Christchurch shooting from the moment it happened. The shooter livestreamed his horrific act and many bad actors continued to upload videos from the stream even as YouTube, Facebook, and others attempted to take them down.

Even though the shooter regularly used platforms like YouTube and Facebook, fringe websites very much played a role in his radicalization too. Tarrant frequented forums like 4chan and 8chan and donated money to far-right websites like The Daily Stormer and The Right Stuff.