There was an old drug store, not part of a chain but run by the pharmacist-owner. A thug walked into the store and pointed a gun at the pharmacist, who promptly pulled his OWN GUN and shot the thug through the heart. There were no charges, of course, since this was in a civilized place.
A couple of weeks later, another thug walked into the same pharmacy and pulled a gun on the pharmacist and announced, "You shot my cousin". The pharmacist promptly pulled his OWN GUN and shot the thug in the heart. No charges. Déjà vu?
Believe it or not, that drug store was NEVER ROBBED AGAIN. I wonder why?