Very sad to hear about all of this. With these things I try to keep away from the news stories for a few days until the dust settles... too much misinformation and hysteria going on to make any sense of it as everyone is still reeling around for information. Not sure if it's just because I'm getting older, or desensitized to it, but I don't see a clear solution to this sort of thing. Full disclosure: I'm a permitted gun owner. Not for home defense or the apocalypse, just for target shooting and having fun. There's a lot of stigma and fear around guns, but most of that melts away once you get involved with them.
I don't really understand why everyone hones in on the "gun issue" when these tragedies occur. I think there's a lot to the mental illness claim, but you'll still have some bad people out there no matter what you do. We've made some major improvements with our understanding of mental illness and treatable conditions over the years. Does this guy classify as having a treatable illness? I wouldn't think so. Perhaps an autopsy will show a brain tumor that could explain part of this- we don't yet know.
What's the root cause of these things, if there even is one? Is it cultural, mental illness, weapon prevalence, human nature?