Good post Future.
In the cases of school shooting, in a majority of those cases, the weapon was purchased legally, so yeah. Its tough if you live in a state where gun ownership is legal and you have zero priors (not even a speeding ticket).
Last I checked, the LAS Vegas shooter just loved to gamble........and he lived in Vegas so red flag not found.
As far as all the illegal weapons in circulation, that's a whole can of worms I simply am not able to discuss as I really don't have an answer to how to combat that. Bad guys don't follow laws
