Another one I'd like to mention is Ryuichi Iwasaki. He wasn't a very well known mass murderer but he killed 2 people in a mass stabbing in Kawasaki, Japan. One unusual thing about him was that he didn't have internet access, but he did have a magazine about mass murders. I'm curious about what caused him to commit the attack.
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"Now! Feel death, not just mocking you. Not just stalking you but inside of you. Wriggle and writhe. Feel smaller beneath my might. Seizure in the Pestilence that is my scythe. Die, all of you."
- T.J. Lane (in his Facebook poem)