Why did Klebold and Harris shoot up Columbine high school? It's because they decided to do so. It's as simple as that. Who is responsible? They are. Since they're both dead, it's an unsatisfying answer. We want someone to blame, someone we can punish. But sometimes you can't get what you want.

Is it possible to prevent that kind of thing from happening again? Yes, but the price is too high. Klebold and Harris and John Walker Lindh are statistical outliers, and when a society is as big and varied as ours is, one in a million is damned well a long way from the center of the bell curve. The only way to prevent that kind of thing is by completely regimenting society in ways I could never accept. Millions of people play violent video games and then go about their lives as normal people; violent games do not make people violent. Millions of people listen to heavy rock music; there are many people whose parents break up or come out, or who adopt strange religions. Nearly everyone's parents screw up one way or another. Ultimately each of us has to play the hand that life deals us, and do the best we can with it. If we screw up, we have to accept responsibility for ourselves. And when others screw up, we have to let them, or force them, to take responsibility for themselves.