First of all, calling that collection of hideous noises playing in a continuous loop in the background is an insult to music lovers everywhere.
Next, it doesn't seem to me that the guy knew the kid. I think he just picked him out and started whaling on him. The kid, knowing he'd done nothing wrong, tried to figure out what was going on and reason with the guy.
Assuming this is even real footage, the kid should have gotten the heck out of dodge as soon as he could. He is young, fit, and lighter than the other guy. He could have outrun him easily. He didn't even need the gun.