In fairness he was asking you to clarify what you meant...
Here's the problem. The only way to know if someone ought to go through that secondary screening would be for the government to examine the medical records of everyone that seeks a gun license. In that one statement there are two, separate violations of the Constitution.
It is not possible to prevent these things from happening. It is only possible to reduce their impact (by allowing people to quickly respond - ie have a gun on them) and to punish those to do commit the atrocity.
MY view is that some people are incapable of existing peacefully in our society as it is today. Since WE aren't changing and since it seems inhumane to lock the poor buggers up in what amount to jails, the alternative is to remove them from that society:
Create throwback communities to 200 years +/- ago. A planned community along the lines of Olde Sturbridge Village, but self sustaining. Work out a plan to help people integrate into that society and find their niche, whether it is farming, blacksmith, teaching, running a shop, whatever. But there's no phone, no tv, SURE as hell no facebook. You get your news by walking down to town common and talking or reading the weekly paper. Yes, we had mud eaters back then but there weren't usually more than one or two idiots to a village.
Hard work is good therapy for many people.
We've forgotten that.