no idea what I would do.... being several blocks away, I would do nothing, but let's say I was at speedway, I am towards the back picking up a nice cold 6 pack... dude pulls a gun on the guy behind the counter.... do you pull gun and go towards the guy trying to rob the place or duck and cover? I think in that situation, I would definately draw my firearm, but I would not go trying to be a hero and shoot the agressor in the back of the head.... now if he shot the clerk and is coming around, my ass is going to pretend I'm playing splinter cell and pick that mother fucker off before he knew what hit him.