On Friday, a man murdered 49 people in Christchurch, New Zealand. He targeted Muslims at two mosques in the city in what’s been deemed a terrorist attack, one of the most horrific acts of violence the country has ever seen. Shortly before the attack, in what appeared to be posts from the alleged shooter, links to a Facebook livestream of the killings were shared on 8chan. Social media channels later struggled to remove copies of that stream, while his 74-page “manifesto” also spread from 8chan across the likes of Facebook and Twitter.