* The scanners would discern between a metal gun and a metal laptop?
* With efficient crowd management?
* Fast enough for an operator to act?
* Act meaningfully?
Howzabout first ending the revolving-door book-and-release fiasco and take note of the effects of keeping a few hundred thugs off the streets and remaining thugs knowing they will be held when arrested rather than turned loose.
Doggone, it, Pete, you're making sense, and you know that doesn't work with leftists.
I just see something like this shifting the scene of the shooting up by the front gate, which might make it easier for the shooter to get away...

You, of course, are right. Lock up the thugs, throw away the key, and quit promoting 'thug life'...but that would mean 'no G' for the 'OG' crowd...