He was a disturbed individual, that's really all there is to it. He didn't just snap and kill a bunch of people, he was mentally unstable. He had a history, but I'm still not sure this could have been prevented. People are targetting the guns because there's nothing else left to target. The students are dead and Cho is dead. There's nothing left to blame except his parents and the guns. I don't think he played video games, so they can't blame that. All they can do is say "Look, he used a gun, let's enact more gun laws to keep this from happening again". What they're all failing to recognize is that they may not be able to keep this from happening again. All you can really do is prepare yourself for the worst and hope it doesn't happen again.