Yeah, "what if" the scenario were different and a CCW carrier had seen him trying to enter the theater with a weapon and body armor. What then?
Or "what if" his weapon had jammed while he was 10' away from someone with a CCW?
Or "what if" a police officer had been on duty in the theater and engaged the shooter, and managed to kill 1+ bystanders? Most police I've met at the range don't shoot that well.
Or what if it was in broad daylight, in a restaurant, with a CCW carrier who was an excellent shooter?
I guess we will never know. But the world's a dangerous place.
"Be prepared", Boy Scout.
Side note: are you the guy that developed the "Active Shooter" CBT for the AF? You know... the one that has military folks hiding under their desks in fear, while the shooter goes room-to-room killing people?