If four or five citizens had holstered/pocketed, loaded semi-auto or revolver hand guns at both the Maine bar and bowling alley, and shooter Card suspected it, he would never have struck. Sociopathic shooters are crazed but clever enough to strike “soft” targets—as they still want to minimize risk to themselves while engaged in acts of self-effacement.

If there were four or five plainclothes security officers with marksmanship certifications armed with semi-auto rifles of their own choice in attendance at the 2017 Las Vegas Aldean performance, Paddock would probably have reconsidered his mass shooting—or at least seen it curtailed before so many people had been shot.

Now we are into the issue of "subjective justice." Attempting to preempt shooters by diagnosis is impossible as mental state is self-governed—and anyone is capable of choosing “insanity.” People with a history of mental illness aren’t necessarily sociopaths and can actually regain reasoning mental health. Maintaining reason and sanity is always volitional—subject to choice—and not automatic or “guaranteed.” Therefore, attempts at “red flagging” individuals to deprive them of weapons—aside from non-citizens—will always be highly problematic.

In my opinion, the 2nd Amendment (along with all other Bill of Rights/Constitutional clauses) should apply only to US citizens, and none should apply to non-citizens. Therefore, “red flagging” non-citizens for weapons possession may be appropriate. Citizens should be immune from “red flagging” regardless of alleged mental state. Only through actual perpetration of crime can criminality be judged and punished. And “mental state” should never be a factor in assessing criminality, only the material facts or evidence of a crime. How can mental state ever be regarded as material or even knowable by any person other than the accused?