There is not even the slightest hesitation to your movements or in your mind. You have faced down desperadoes and bandits before and you have shot men down. You are prepared to do so again. You skin your revolver in a quick motion, cocking it as you do. At the same instant, both of the men scramble to get out of your line of fire, moving to draw their own pistols. A moment later the the air around you is filled with smoke and the deafening report of revolvers going off.
Your first shot catches the first man - a big, hairy, nasty looking fellow - in the arm and he spins at the impact, taking his revolver off-line with you. You're moving to the right now, eyes focused, and you hear the report of another revolver and feel something nick at your coat. Your second shot catches him again, right in the midsection, and he folds and crumples to the wooden sidewalk with a groan.
Next man. There's another shot, another miss, and there's screams from around you as people scramble to get out of the way. Shouting. No time to think about that - your blood is up and the world has narrowed down to this last obstacle. You fire and you miss, the bullet taking a chunk out of one of the support beams of the building's overhang.
Last bullet.
You fire and it catches him in his right wrist. The man screams aloud as his gun drops to the floor.
Your gun is empty. He doesn't know that.
As he starts to scramble for his dropped pistol with his left hand, you step forward, jam the barrel of your pistol toward him, "If you make another move, I'll turn your head into a canoe."
The man freezes and stares at you with a look so hateful that you swear it could curdle milk. From off to your right, you hear the other man moaning, "You've killed me - Tommy, she has killed me! O Gawd, I am shot to pieces--!"
There's a racket coming from behind you, the sound of booted feet and yelling. Probably the sheriff.
[ ] Stay and explain. Even if you technically shot first.
[ ] Grab your horse and whatever else you can and get while the going is good.
[ ] Indulge in some retribution while you wait. His face would look better with your boot moccasin in it.