Sounds like trying to express a good idea, but just can't quite latch onto it.
Let me help.
It appears in this case, and in several others, that school shooters are often alienated from the rest of the school which they attend. Granted that some of it comes from their own already odd behavior, but really, you think you see someone acting odd, and you constantly pick at them about how they're not exactly like you, and everything is going to be sunshine and roses? No, you're telling someone with possibly already disturbed thoughts that they're useless, and dangerous, and shouldn't be there, or anywhere, with any humans.
Ask yourselves, how many of these kids are called psychos and terrorists for years before they snap?
So, okay, I can see that point. Going in and shooting up the school is obviously a horrible solution to the problem, but so is having basically everyone around a person with problems that because they have problems they should just go and kill themselves. Are Hogg and Gonzales responsible? No, not really. Could they have done anything that might have prevented it. Possibly. As could everyone else in the school, by offering at least a friendly ear, give Cruz someone to talk to rather than tell him, over and over, that no one cares about him.
Now, you might say something about the problems he obviously had even before bullying and alienation was an issue. Name one person who doesn't. This is why you don't push people around and treat them like crap, because we all have this potential.
By the way, I can tell you from experience, a lot of kids are bullied and alienated by the kids are ignored by the adults. So tell a teacher was not really an alternative. The teachers too often believe the crap told about how dangerous someone with these kind of emotional issues is.
Another thing to remember . . . a lot more kids have these problems than ever go out to kill anyone. But hey, some of us get to smoke pot with our older brother and his friends, maybe that makes a difference.