Jeff...
This kid seemed very angry at something, be it the Bush (Read his reviews to understand this part), his grandparents, or the people at school.
I always find it senseless when people do something like this. I know how it feels to be a teenager (I am one right now). It sucks sometimes, and sometimes it doesn't suck so much.
People are idiots, it's not that hard to figure out. For whatever reason, this kid decided to take his anger out on everyone else and lose whatever future he had in store, and the future of the people he killed. I can never forgive any for doing something like this, but I can always wonder why somebody did this, because no matter how much you read his work, watch it, analyze it, or watch the news stories about him, you will never truly figure out why he did it, because only he knows why.