I am assuming that this question was posted for academic purposes only. We are discuss 'how many times' we would shoot someone. Folks, come on, we are talk about as it we are shooting at paper targets.
IT'S A HUMAN LIFE we are discussing here. How many of those that have posted a respond have been in that situation? what else was going though your mind at the time? was it really how many times I should pull the trigger? there are other moral, legal and religious considerations here.
I think a better question would have been, "how many practice the double tap verses a single shot", for when the time comes, I KNOW you won't be counting.