This might be* stupid, but hear me out.
One of the problems with guns is that for all the fancy gadgets and accessories, they are pretty low tech. You can put a laser site on a rifle. It's still just an enhanced version of a very old technology. It's a technology that is so old that it is not networked in any way. It cannot be controlled from afar any more than a hammer or hacksaw can be.
We've been talking a lot about biometrics that would prevent anyone but the legitimate owner from firing the gun. That strikes me as a credible idea. But, it does nothing to stop a legitimate owner from committing crimes or killing people. As we've been told, most spree shooters are, if not legitimate gun owners, could have easily passed the various screens in place to get guns. They don't have priors, for example. The spree is their first, and last crime.
If you want to stop spree shootings, you need to retrofit all guns with a networked device that police can use to turn the safety and lock the gun down from afar. Is that... far fetched? I'd submit that the technology exists to do this.
The complaint might be that this would disadvantage civilians in a gun fight with law enforcement. I don't much sympathize. Even in cases of police abuse (false arrest, harassment, etc.) you're expected not to combat law officers but to seek legal recourse after the fact. If a cop walks into my office right now and places me under arrest for a crime I know I didn't commit, it is not my prerogative, no matter how wrong the officer is, for me to knock him down and put him in a figure four leglock. If I do, I've committed a wholly separate crime.
So... remote gun deactivators, run by law enforcement, on all new models sold going forward and retrofitted on all models out there with severe penalties for non-compliance.
Why the heck not?
* "will be"