I'm not sure how much that applies here. Killers with manifestos have always existed, it has little to do with the internet. They were always in people's faces

I'm not sure how much that applies here. Killers with manifestos have always existed, it has little to do with the internet. They were always in people's faces because, well, they killed people and left manifestos. Where the internet does come into its own is allowing these disturbed people to find other like-minded (like-disturbed?) people, and feed off each other's misery, perhaps making them more likely to kill.