Again this has nothing to do with what you think only with what he thought in that split second.
It has all the appearance that his wife was trying to hold him back from attacking the elderly retired gentleman by restraining him physically. She put her hand on her husbands chest to hold him back. She didn't grab him and try and pull him out of the way.
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???