I blame the media. No games and music and such, but the news. If a person couldn't get attention by blowing up a school, would they be doing it at all? Stupid stuff happens all the time. The problem is that the media finds these people and reports them when otherwise it would have remained a shameful family secret. In turn, this causes people to be scared, and that creates stress that some people might end up acting out in the form of other stupid things. Then THAT gets reported, and the cycle is never ending. I think that's why they don't report suicides except in high profile or unusual circumstances, like somebody going spat on a subway track.
I am starting to think that people violent video games to give themselves a break from all the pointless killings and stuff, rather to engage in it.