If a person threatens you with a weapon, why don't you just shoot him/her before it does get out of hand? What if the weapon was a knife? I understand confrontation's with a knife usually get the officer cut up pretty bad.
Funny thing for me. When I was in Europe in the service, we were out on a training mission in the field. I was on guard duty one night and all hell broke loose, a whole lot of rifle fire! Turns out the unit training us got a bunch of blank ammo and rushed out parimiter fireing full auto weapons. Our guards on the perimiter folded right there!
Imagine if you'd have come into contact with those two holding weapons and opened up with blank ammo! You'd probably be in a lot of trouble but I can imagine the looks on their faces!