These events can only be minimized, never eradicated. Evidence has shown that reduction of the number of events can only be achieved by arming more responsible people to counter the irresponsible and mentally unbalanced.
O.A.

People and Groups will always lasso a tragedy to further their agenda. As posted here in the Gulch, it is a fact that gun free zones are targeted for mass shootings. So the very thing they are trying to accomplish, safety, is compromised by the premise.
Mental health. I believe there is a component in the decision lock of these monsters for the fame media will provide and power over the powerless. Both are achieved in one fell swoop and not by rational means. The power is short lived but the infamy remains. I do not buy into the concept that all are mentally ill. In the Colorado shooter's case, there is evidence showing a mental disorder and medication needed and he was not adequately supervised given his disorder. When one looks at Columbine, there is no such evidence. In the case of the Conn shooter, I don't think there is enough evidence yet to know. There are monsters and evil in all societies and the evidence is clear that in the US there are no more of these events(excluding war and terror attacks) now then at any other time. (There was a spike in 1929 that I'll put down to Prohibition).

Your question reminds me of the theme in an old ad campaign of the Caterpillar Tractor Company:

"There are no easy answers. Only intelligent choices."

Methinks it said it all.