I'm going to try some amateur analysis here and if I'm full of fecal matter, I can be pretty sure somebody will tell me. So here goes:
The national dialog seems to be largely dichotomous - it's either about better gun control or it's about better mental health services. I'd add a third dimension. We have a sick culture here. And I don't limit that to so called gun culture.
We seem to worship all visible trappings of success - money, fame, power and the will to use it, sexual desirability. We have a concept of what it means to be a real man that entails never showing weakness, a robust physical presence and never admitting defeat. Many of our heroes appear to be psychopaths - the world revolves around them and they have no concern for anyone else. We have a media culture that throws this into our faces every time we look at a a screen. Our fascination with video games has adults, who should have long outgrown this, essentially playing electronic versions of cowboys and Indians shoot 'em up games. And some people - nearly all men and nearly all lacking such markers for success, and still playing children's games on a computer - look at this and label themselves losers. And they very much externalize the reasons for their status. It's women who ignore them. It's jocks who belittle them. It's employers who won't give them a chance or who fire them. It's college faculty who don't see their pain and/or their genius. And it eats them up and they get angry and want to do something about it.
Take all this rage, add guns, and watch what happens. We do need better gun control. We do need better mental health services - although mental health professionals are no better at predicting who is going to snap and shoot up a classroom than anybody else seems to be. But absent some discussion on how we view and portray success, we are going to continue to create the sad, sick twisted, rage filled and vengeful types who want to make the rest of us pay for their misery.
And how we do that, I have no idea.