You can't be serious --
What he thought in that split second is what this is all about and that is expressed in his words "that'll teach you to throw popcorn in my face".
That means that he wasn't shooting him out of fear but out of vengeance instead.
Even the shooter's wife in response to it said "that's no reason to shoot him".
She put her hand on her husbands chest to hold him back.
If she was holding him back then he had no reason to act out of fear. So then why did he shoot the person holding him back and the person being held back???
He could not see what they guys wife was doing he had a face full of popcorn. He was reacting to the physical assault. His wife's perspective, view of the situation was unobscured by popcorn so she did have a different assessment of the situation than he did. She saw what he could not see because he had a face full of popcorn. He reacted on what he knew and saw. There is not time to have a discussion in a reactionary "shoot no shoot" situation.
This will all come down to if he can convince a judge or jury that he was in fear of great and grievous bodily harm or death at that split second in time. None of this will be about what other people with better vision of the situation thought. He did not have that view or that knowledge at that time.
I don't put any significance on his statement later. I've been around a lot of cops and they always make smart-ass cynical remarks. That is how they deal with bad situations no matter if they are involved or not. That is just a cop being a cop.