You mean a concussion.
Blunt trauma is injury where skin is not pierced and no extrenal wound or bleeding occurs.
Penetrating trauma is injury where skin is penetrated and a visible external wound happens.
Perforating trauma is when there's both entry wound and exit wound.
Concussion is bruising of the brain resulting from rapid acceleration of the head, and I wasn't really referring to that. In indoors distances, a four-foot staff would likely be a very effective weapon provided you could use it. It has a good reach and if you have some training, most people would not have time to react to you striking at the gun to point some other direction than you, after which you could proceed on to disarm them or to whack them with your stick some more... And as far as lethality goes, a thrust to larynx or abdomen is nothing to look down at. Third and probably least lethal debilitating point is obviously the groin.
Besides that, how many burglars actually carry firearms? And how many are dumb enough not to keep a stakeout for the target house to confirm that no one is at home? Granted, the dumb ones probably are the ones that carry the firearms... but regardless, if you want to defend your home and family, get some decent alarm systems rather than a gun, which a sensible person would keep in a secure locker with ammunition stored in separate place and thus negating it's ultimate usefulness in a home-defense scenario...
Four-feet staff under the bed would be my preferred home defense solution. With a proper alarm and lock system. Moat couldn't hurt either, coupled with electric barbed wire fence and camera surveillance systems. With towered guard positions. And booby traps along the most probable approach routes.
All of which would be more effective defensive solutions than having a handgun.

Regarding school shootings... it boggles the mind why them guys don't end up dogpiled and disarmed in a short timespan. Probably panic mentality and lack of leadership, but still...
And as far as the phenomenon itself goes,
nothing new with young men flipping out and going on a killing spree; it's just that with the increased ease of aquiring lethal weapons the consequences are all that much more severe...