The New Zealand Royal Commission just released its report on the 2019 Christchurch mosque attack. It concludes that the shooter was radicalized on YouTube. https://www.theguardian.com/world/live/2020/dec/08/christchurch-shooting-royal-commission-report-to-be-released-live

I still remember the night of the shooting. I was sitting at my dining room table, watching the news come in. I read the manifesto. I saw the 8chan post and the Facebook livestream. I heard the shooter say "subscribe to PewDiePie."

I don't typically cover terrorism, but I felt moved to cover Christchurch because of how horribly *online* it was. All the in-jokes and chanspeak, the way it was designed to go viral. I'd never seen anything like it.

At the time, my theory was that the shooter had been radicalized on YouTube. But I couldn't prove it. All we had was the manifesto, and whatever we could glean from his background.

I couldn't interview the shooter, obviously. So I started looking for people who could help me understand how YouTube radicalization works. I found Caleb Cain. And we wrote a story -- and later, made podcast episodes -- about how Caleb fell into an alt-right rabbit hole.

It was a fascinating story, involving all kinds of characters Caleb got attached to: Stefan Molyneux, Lauren Southern, Richard Spencer. My colleagues and I spent the better part of a year exploring and explaining far-right YouTube, sketching the pipeline.

YouTube radicalization became a big story. There were op-eds, academic studies, conference panels. YouTube made changes to its recommendations algorithm (after denying it was a problem). But we still didn't know how the Christchurch shooter was radicalized.

Now we do. As the full report makes clear, the Christchurch shooter was a YouTube radical. He watched tons and tons of far-right videos. He sent money to Stefan Molyneux and Richard Spencer. He donated to Lauren Southern's media company. https://christchurchattack.royalcommission.nz/assets/Report-Volumes-and-Parts/Part-4-The-terrorist.pdf

I'm glad that YouTube has (belatedly) changed its policies on white nationalism and hate speech, and that leaders like Jacinda Ardern are pushing them to do more. But we missed an opportunity to take this stuff seriously when it mattered. We can't do that with the next platform.

Here's our story about @Faradayspeaks, in text ( https://www.nytimes.com/interactive/2019/06/08/technology/youtube-radical.html) and audio ( https://www.nytimes.com/2020/04/16/podcasts/rabbit-hole-internet-youtube-virus.html).

It's not exactly what happened to the Christchurch shooter (and Caleb got out of the alt-right, thankfully), but their YouTube trajectories overlap quite a bit.