You mean it is not OK to shoot someone texting (or otherwise using their cell phone) in a movie theater? It ought to be.
Long line this AM at the cable company when I tried to swap my router. I did not mind the person a few spots ahead of me talking on their cell phone as they waited and inched forward. But when they got to the window and told the person behind the glass to wait while they finished their conversation I sort of lost it.
What made me feel better about speaking up and telling the person to put the phone down and get her business done so the rest of us could do the same was that at least 2/3rds of those standing in line spoke up and agreed with what I had said. (I managed to use only socially appropriate words, although I was tempted to use some what would not have been.)
The thought of shooting them never crossed my mind, although the means and opportunity were there.
stay safe.