If adrenaline is rushing, you will not notice the passage of time like you do in a calm state. You could empty the magazine before you knew it.
And why should any FREE man RUN from his attacker when he has the advantage? Why the F would you turn your back on such a person? Are you nuts?
YOu shoot to stop the confrontation, if the other dude ran away, fine. But if he stood there, you shoot until he's stopped(either down or running the other way.)
The only disagreement I have is that you should leave a few rounds for his buddy (in case he is not alone). That is what I was taught in my CFP class. But I wasn't there standing in front of someone pointing a gun at me so who am I to judge his actions?