The Australian white supremacist who killed 51 people at two mosques in Christchurch, New Zealand was radicalized by YouTube, according to a 792-page report on the March 2019 shooting shooting.

This is not the first time YouTube has been linked to radicalization and white supremacist content. The combination of a business model that rewards edgy content and a personalized algorithm meant to keep viewers hooked is a recipe for radicalization.

The YouTube citations are part of a larger inquiry into the hate crime. The shooter sent an email to parliament, the prime minister’s office, and news outlets before he began his attack.

His manifesto was also posted to 8chan, a message board that often hosts far-right content. Included in the post was a link to a Facebook page, where the poster said a livestream of the attack would be broadcast.

A 17-minute video that appeared to show the shooting was uploaded to Facebook, Twitter, and Instagram. The video and the manifesto were re-uploaded repeatedly over the following days, often faster than platforms could take them down.

The report goes on to say that though the shooter frequent far-right message boards on 4chan and 8chan, the evidence shows a more substantial use of YouTube. The shooter also modified his firearms before the attacks using YouTube tutorials.