I am not sure how these kind of things can be prevented at public universities. There does not seem to be an easy or even extremely difficult solution.

I suppose you could put undercover (armed) marshalls on campus like they have on airlines? I would not trust arming many of the undergraduates I have been around at the number of campuses I have been on since 1976.

I also know that in some countries people who do not agree with the status quo might get labelled "mentally ill" by those in power and carted off to the gulag. Happened a lot in Nazi Germany as well as in Stalin's USSR and well as various other countries. Allegedly it happen in China not too long ago as well.