I woulda shot him too.
In a heartbeat. When some strange person sucker-punches you to the ground and then gets on top of you and starts banging your head into concrete, your only assumption can be that he means to either kill you or do you serious bodily harm. You don't have time to intellectualize over the finer points.
I'm reminded about a joke involving a girl named Mary Ann. It seems that Mary Ann was walking down the street one night when a big black dude came jumping out of the shadows and started ripping her clothes off. She wasn't worried. She knew she had left her wallet at home.
Somebody would have sooner or later. Maybe after he shot a few.