Body armor, backpacks, baseball caps, etc. have all been marketed/sold and then stories written about them (driving both fear and sales) after shootings in the past. It also has driven the opposite craze, with the increase in AR parts, and gun sales (my local gun store sold around 60% of their inventory last week). Shootings drive both groups to spend money, the questions are always who gets the money and what do they do with it.
We (the general population) did give away quite a lot, by reacting, instead of having patience, and taking time, and agreeing to the patriot act. Now while trying to direct some of that to go away (NSA keeping stuff), we make it a profit center for businesses to keep all their data for the government.
You could own a ship full of cannons back then (the equivalent of a battleship). When the Constitution was written, well look up the Girandoni air rifle (the automatic weapon of the day). As for young men attacking a school full of children, look up Indian massacres. They were familiar with wipe outs.
As for people with mental instabilities getting guns, legally, of that I am on the fence. I KNOW the person that caused Missouri law to change. As an armed guard he shot out the rear window of a fleeing suspect, that had stolen a bottle of liquor. He was given every opportunity to show defense (was their backup lights on, etc) and didn't comprehend anything wrong. His dream was to be a cop (and it was also his nightmare of being shot as one), and back then, the condition was known to us, only as mental retardation. (I am not family so never heard a clinical diagnosis)
Where I am on the fence is who gets to decide and exactly what are the criteria? If you see someone talking to someone that isn't there, can they have a gun?
What if you don't see the Bluetooth headset?
What if they are driving a car that says in god we trust and are praying they don't get shot that day?
Who gets to be the inspectors to the inspectors and what are t heir agenda's?