My only direct experience is with federal courthouses, nearly all of which have armed Marshalls and metal detectors at the entrances. All bags and packages are opened and examined, everyone goes through the metal detector. Some of the larger courthouses repeat this on every level as you step off the elevator. Some even do it at the entrance of every active courtroom.

A system like that creates a host of problems for a hospital, but guards and detectors at certain strategic points might be worth considering.

IMO it is more effective to keep the armed aggressor out than it is to control him once he and his weapon are already in.

Frank2135