I know the last thread turned into a political debate or something like that but this article was pretty interesting.
I've always been very aware of PTSD and it seems like we might have figured this one out:
"In a screenplay Cho wrote for a class last fall, characters throw hammers and attack with chainsaws, according to fellow students in the class. In another, Cho concocted a tale of students who fantasized about stalking and killing a teacher who sexually molested them."
BINGO. I could be wrong and these sorts of things are hard to prove but I'm guessing this is where the problem stemmed.