He could have moved to another seat. The conflict would have ended there. Shooting a gun in a theater without a clear, immediate danger to your life, is grossly irresponsible & risks the lives of the audience. Popcorn is not a clear, immediate, life threatening danger - far from it. Had the texter wanted to hurt the guy he would have thrown his fist, not popcorn.
If you go to a movie intent on an enjoyable evening & your seating neighbor is being disruptive, why would you increase the disruption for everybody by having a verbal altercation? What authority do you have to stop your neighbor from texting or talking or being a disturbance beyond Shhhh? Regardless of outcome, wouldn't such an argument pretty much ruin the evening for you and everybody nearby? Wouldn't a simple seating change end your problem quietly & immediately?
Now, let's say the texter was, instead, two women giggling & talking. The retired cop asks them to be quiet, but they curse at him & throw popcorn at him. Is he then justified in pulling a gun & killing them? How about 2 kids? When does the guys actions become unreasonable, if ever?
As for popcorn throwing, it is an age old juvenile custom in theaters. I doubt anyone considers it a deadly assault except those who shoot someone in a theater.
The idea that personal offense for a minor disturbance is justification for extreme violence is barbaric. Whatever happened to turning the other cheek, moving to another seat, asking for your money back, or just ignoring the minor disturbance? This is the very same mindset as Liberals have: That any PERCEIVED offense is a crime deserving extreme punishment.
If you are in an argument with someone and they are making threats and they throw something in your face and you protect your eyes by closing them how do you know they will not follow up with a fist?
..like being cut off in traffic, or having someone with 11 items in the 10 item line, or using the last bit of TP without replacing it, or taking the last scoop of mac and cheese at Golden Corral, you know, all the really BIG annoyances out there..
..well, there would be millions shot and killed because every day there are annoying people in our lives....