I hate to be pessimistic, but I don't think that the human race could handle peace. If you look throughout history, mankind has just picked stupid little reasons to go and create conflict. It's just our nature. It's sad, really. There are a lot of people who are happy, peaceful "hippies" (I try to be), but there are just enough bad-willed people who ruin it for the rest of us.
I am in no way supporting their actions, but they could have possibly been prevented. The parents should see signs of their children going off-track, you know, in the dangerous ways? Also, school counselors should see a few hints on the matter. As for guns, why would you keep a weapon AND it's ammunition out where people can get to it?
While I was growing up, guns were not a new thing to be. My dad hunts deer, and every year I saw him cleaning his rifles. I even helped him clean them before I was old enough (or tall enough) to see over the table. He taught me to NEVER touch them unless he was around, even though I never could because he always had them locked up. I was taught gun safety, and when I was old enough, he took me hunting. I got to first-hand see what a gun does to a living thing. I got to see the damage and saw the deer die. I never would have thought to shoot a person (or anything living).
My mini-theory is that some kids only experience guns from a video-game or movie standpoint. They press a button and BOOM, their problems go away. No fuss, no mess. It's just a bunch of red pixels that are washing their problems away. For people who are mentally disturbed because of social inadequacies, this may look like a good option. It's just my opinion, you can take it or leave it.
That's just my :twocents on the matter...