Throwing popcorn was the trigger event, but the guy was being held back by his wife which seems to demonstrate to me a continued escalation of aggression. Combine that with being in a dark theater and not being able to fully analyze the threat. The shooter's response was certainly reactionary but far from murderous.
Don't start physical **** with somebody unless you are prepared to reap the consequences, legal or not.
No him texting was the trigger event. From CNN
"Charles Cummings and his adult son were two seats away. Cummings said that when Reeves returned to the theater, there was no manager with him.
"He came back very irritated," Cummings recalled."
And then
"Voices were raised. Oulson threw a bag of popcorn at Reeves, police said. Then, the former police officer took out a .380 semi-automatic handgun and shot Oulson."
And
"Voices were raised. Oulson threw a bag of popcorn at Reeves, police said. Then, the former police officer took out a .380 semi-automatic handgun and shot Oulson."
I dunno about you man, but I don't consider throwing popcorn to starting "physical ****" that's like saying someoen poured a beer on their head so it's cool to shoot them.
I have not read a report that he was being held back by his wife, but who knows. As far as the setting, you're right, but it's not an excuse for deadly force. Unless he was able to see a brandished weapon, there's no reason for deadly force.
Deadly force is the key, using deadly force as any cop would tell you is a last resort. For this guy it was his first resort, not a good thing.