You don’t get to kill based on mere possibility. And you would not like living in a world where you could.
The patron had plenty of room to retreat. Plenty of time to give a better warning, such as “stop or I’ll fucking kill you.” If a person keeps coming after that sort of warning, that’s a fact from which the inference a threat to life is more reasonable; a person with no fear of death.
This dude had a phone in his hands. Didn’t take a swing at the guy. Didn’t persist with no apparent fear of death. The patron pulled out the gun and fired instantly after merely saying “stop” three times.
I accept the jury was in the best position to decide the facts and apply the law. The dude was charged, stood trial, and was only partially aquitted. I rest my case.