Funny, my spellcheck doesn't like either Bobert (or my last name!).
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I agree with Stim that it is near impossible to deal with deranged, intelligent minds.
These individuals are not in crime registers and often seem normal (if perhaps loners) to us.

We can't demand that everyone has periodic mental examinations.

Weapons control doesn't help much since it is easy for the intelligent mad to fashion a murderous device using household and farm chemicals and fertilizer, even if guns are forbidden (moreover, a number of hobby metal workers I know would have no problem whatever in making a viable gun).