In every one of these school shootings, I hold the parents accountable for them. If parents paid more attention to their kids and didn't try to fob childrearing off on teachers, tv, and video games, they just might have seen that their kid was bugnuts.
I also blame society for taking away the outlets that boys need while growing up. They need an outlet to vent the testosterone and other hormonal crap going on. When I was a kid, the boys were rough and tumble, getting dirty, wrestling each other, building forts, playing cops and robbers, playing sports without parents helicoptering over them. Society has tried so hard to erase the gender lines that it's become taboo to be a normal boy or girl for that matter.
If your kid is dangerous, do something, don't go out with friends and hope that your kid will 'be alright'. It's hard, but if your kid needs to be committed, be responsible and do it. Don't make innocent people pay for whatever lie you told yourself to make things alright.