As a gun owner, you have to be cool-headed, more-so than the police ever have to be. You do not ever run around pretending to be the police while carrying a gun because then, stuff like this can happen. You do not start stuff, act aggressively, flip the bird, roll your eyes, talk smack, or even raise your voice to anyone, ever.
A combat instructor (who happened to be Buddhist and a Marine) once said to me:
"From now on, when dealing with (ed.) crazy / possibly violent people, you will lose every argument. You are always wrong. You are sorry for impinging on their day.
You will apologize and apologize again. You will back the heck down. You will put your tail between your legs. You will let them talk stuff about your lady friend. You will let them call your mother a witch and a hooker, your dad a punk.
You have no ego. You do all this because if you are the one to start a fight, by default that fight now has a gun in it, and if you start losing, you're going to pull it and kill him.
Even if you don't go to jail because you could convince the jury that it was self-defense, you're going to have to live with the fact that you took someone's life in defense of your pride and ego not your life.
You are not the police, so don't act like them. Though many of you [civilians] are better shots than the police, you do not have the training, the continuum of force policy, a union, plus free lawyers protecting you if you screw up.
In closing he added “After backing down and trying to apologize, if at any time you then feel your life or that of a loved one is in danger, put three rounds into his [cardiothoracic] vault, call the police, call your lawyer, give a statement, go home, and sleep like a baby. You did all you could for your attacker, and he was the one that made the final decision...... to kill himself."