I think it is time to put our cards on the table.
The Problem:
A mentally ill man bought a gun legally and passed an FBI check. He murdered 6 people, and seriously injured 14 more.
How could this have been prevented?
He was mentally ill and many people apparently knew about it. He should have been hospitalized, simple as that. Apparently many people were aware of his condition and did nothing about it. That is the mistake that was made.

Constructive solution:
We have mandatory reporting laws on child abuse. Maybe we should have the same reporting for mentally ill people, instead of privacy laws, so that the schools, the military, and other officials would have been required to report him to authorities so they could have had him evaluated and hospitalized.
Once hospitalized he should not be released until we are CERTAIN he is not a danger to himself or others.

Not the solution:
Gun Control: I have personally dealt with cases where mentally ill people seriously injured and killed innocent people with knives, bats, and their bare hands.

Blame the political discourse:
The sheriff in Arizona is blaming the vitreal political speech. When he has been asked yesterday and today what proof he has that speech had anything to do with this crime he admits he has NO PROOF.
We have a constitutional right to free speech. I have no problems with the current restrictions on speech because they do not restrict just speech but prohibit crime committed through speech that is INTENDED to harm. Just like we have a right to bear arms, we have no right to shoot people without justification.
Who's free speech do we restrict, who decides, and how do we define the restrictions so people know what they can and cannot say, and what punishment do you suffer if you say "the wrong thing"?
People are responsible for their own actions.
If we go down this road there are thousands of people on both sides of politics that we will have to arrest. God help us.