I hate to side with big surveillance, but if I was in law enforcement and wanting to prevent the next school shooting (I’m assuming somebody in law enforcement would like to prevent the next school shooting, right?), here’s what I’d do: make a list of all white males who are currently in High School or have graduated in the last couple of years. That should be easy to do, schools keep lists.
Look them up on social media.
Flag any of those who are obsessed with guns, have few close friends, are members of hate groups, or post statements on line about how they’d like to kill everybody.
It might require a bit of manpower, but most of the work is done on the computer so you don’t exactly need a Sherlock Holmes. You can take some traffic cops who are mostly just harassing motorists, and pull some people off the marijuana detail, since it’s almost legal anyway.
Then, you send Social Services round to their house for an interview. Maybe, if the kid doesn’t do well in the interview, try and convince their parents to get rid of their guns. Something like “Mrs. Jones, your boy is a weirdo. We think there’s a good chance he’s going to take one of your guns and go kill a bunch of people. Maybe it would be for the best if you just turned them over. We’ll let you have them back in a couple of years, after he’s moved out or is no longer a threat.” “No, I’ve got my 2nd amendment rights.” “Mrs. Jones, if your kid does kill somebody with one of your guns, we’ll charge you with accessory to murder.” “O.K., they’re in the closet.”
If that doesn’t work, watch the little fucker like a hawk.