>>But sometimes they decide to send the kid to college and hope it all works out.<<
How do you stop an adult?
This shooter got fed dollars to go to school.
How does mom stop him?
Depends on if mom truly believes he'll become a mass murderer.
As for how to stop mass murderers generally, if ten percent of the audience was carrying, forty people would have been pouring lead into the sunuvabitch before he could get off his second shot.
And the NEXT crazy bastard would know about that and think twice before he shot people.
Oh, they're crazy, so they wouldn't think twice?
Then why did THIS one surrender when the cops showed up?
Hmm, maybe so he wouldn't get SHOT?