@#1485327:
You Are Wrong. There is no convincing evidence of mental illness on either the part of this shooter or his family.
His mother may have been a survivalist gun enthusiast. That does not equal mental illness.
Go look things up on Wikipedia.
>>You cannot honestly say that there aren't people who commit violence because of mental illness.<<
There are a few such people. But that is a very small fraction of the population. And, again, the fraction of people with mental illness who are victims of violence because of their illness is several times higher than the fraction of such people who will become violent.
>>The fact is, some forms of psychosis & ASPD do include tendencies to violence. <<
Those tendencies are slight, although statistically significant (although for psychosis in particular the evidence is marginal - http://www.ncbi.nlm.nih.gov/pubmed/19702378). And even trained therapists do no better than random chance at predicting if individual patients are likely to commit violence, absent indicators such as threats that are not specific to the mentally ill.
And, to make things very clear: those cases you describe are a small fraction all severe mental illnesses.
As I said, better and more available mental health care would be a good thing for many reasons. But reducing gun violence is not one of them. The way to do that is to reduce the number of guns.