Same question to you, 5150 Lego. Anything could have been happening in his life to drive him to this - domestic abuse and stuff. You can't assume he was pure evil or anything - there's usually a reason, and even if it's just insanity or similar, there's usually a reason behind that too. I'm not saying we should have total sympathy here, 'cause yeah, he killed innocent people, but at the same time we have no idea of what was going through his head and why. Sure, it's a possibility that it was for no reason and he did it for 'fun' or something, but still, it can't be assumed.
IMO, we should feel for all those involved, including the survivers who saw their classmates and teachers be killed.