The texter was engaged in a physical attack. Should the person being attacked take notes or ask, how far are you going to take this attack?
The person who happened to be 71 has the right to defender himself. The attacker guessed wrong and was killed. Too bad.
Throwing popcorn is not deadly force.
"The person who happened to be 71 has the right to defender himself."
No, you cannot use deadly force to defend against an non-deadly force attack. Sorry. If you do it you are going to find yourself charged.