We have plenty of retards here, but criminals that have guns are usually selective and not random. You still get the odd incident (like a crazy guy in the country building bombs in his shed, blows himself up) but you never have a kid turning up to a school and shooting a heap of people. And there aren't any "sniper" incidents where a dude gears up, picks a spot and picks people off.

You restrict what the average person has access to and they're only left with their body and random day-to-day objects. People are still killed inadvertently obviously, but even cops have less reason to shoot simply because "the guy was going for a gun".