I think you misunderstand me, I don't think they should be held accountable for their kids shooting people. I don't think parents should be held accountable for their kids misbehavior be it mild or extreme, as you said raising teenagers is tricky and most any teenager is going to get into some kind of trouble.

But I don't believe a kid gets so disturbed that he kills a bunch of people and himself without having gone through wholesale abuse, the parents should be punished for that. And I do think that when you get hints that that might be going on, like when a kid has a story where everyone in their school gets killed or they have a website that outlines how they want to kill everyone, the parents ought to be looked at first. And I'm not saying that you use the kids acting out as proof, I'm just saying it's probably cause to look deeper. If you can't find anything, then the parents are off scott free.

Maybe I'm just old fashioned but I think arresting kids should be the last resort after you've tried to treat them and or rehabilitate them. Sure, you can't always do that but don't you have to try?