The oldster didn't just kill him. He asked the vic a bunch of times to stop it, argued with him, got up to get a manager, evidently the manager gave no fucks, oldster returned and continued the argument, someone threw popcorn. Some things they said give clues as to what went on.
For one, the vic's wife was injured because she put her hand on the vic before he was shot. Which means they were probably standing up, at minimum they were turned around in their seats. It also means the shooter caught her in the hand or arm and the bullet went through and into the vic, slaying him.
So we know there was an argument. We know the shooter fired. We can make some other assumptions.
1: The range was very close. Normally I would say that a 40-yr-old would be able to move in and strike a 70-yr-old before he could draw. But the seats are in the way which could make all the difference. Also the woman had her hand on the vic, and the shot struck her and the vic, which means the vic had not advanced far enough to make her hand slip aside.
2: If the vic had thrown the popcorn, it was either an insult, or a feint to avoid getting shot, or a feint in order to attack.
3: If the vic's wife threw it, it was probably an insult but may have been a feint, perhaps on behalf of her husband. But her other hand was busy, and she was evidently trying to hold the vic back, which suggests she wouldn't be the one throwing. Why would she?
4: If the shooter threw it, it was certainly a feint to attack. He was about to attack and there was no reason to throw it otherwise. But he had a hand busy with the draw. You don't throw popcorn and then draw; the popcorn will begin falling before you get the gun into position - especially if you're 70. Also there doesn't seem to be a benefit to feint to attack using a gun. You already have all the advantages.
5: If the shooter's wife threw it, it was most likely a feint to attack on behalf of her husband. She knew he was carrying, she had to. And we don't see her in the argument report, so she's unlikely to be incensed enough to throw it as an insult.
Because of 2-5, I assume the vic threw the popcorn. But did he throw it before or after the gun emerged? Did he throw it and lunge forward, prompting the shooter to draw and fire? That's not likely, because the vic would have advanced enough to clear his wife's hand before the 70-yr-old shooter could draw and fire.
Because of these things my assumption is that either:
A: Shooter draws, vic throws popcorn to distract, shooter hits him anyway, or
B: Vic throws popcorn to insult shooter, shooter draws and fires.
Either way this guy is in a pickle. It'll hinge on self-defense, fighting words, and what the shooter alleges the vic did immediately before he drew.