UPDATE[Cliff Notes]
Turns out he was a member of a website called vampirefreaks.com. In the days leading up to this he posted chilling material (himself in costume, with gun), calling himself the angel of death.
Quotes he wrote included things like:
"Work sucks … School sucks … Life sucks … What else can I say?" he wrote. "Metal and Goth kick ass. Life is like a video game, you gotta die sometime."
[/Cliff Notes]
Don\'t you just KNOW they will focus on the video game part of that sentence, as opposed to the much more blatant anti-social behaviour (goth/vampire worship, piercings, mowhawk) he participated in.