“However, even an old SWAT officer ought not to have been in “fear of his life” from an attack by popcorn.”
Throwing something in an opponent’s face is a good opening move in a fight to blind, distract, or startle them, followed up by an attack or attempted disarm. A lot depends upon the details, especially how quickly after the popcorn barrage the shooting happened. Hemmed in by people in a row of theater seats, one is unable to retreat or flee.
Of course the shooter could just be a dumbass.
I think you're on to something there...