So the 'bully' was walking towards a guy who had armed himself with a loaded gun and videocamera. The bully wasn't charging in a menacing manner or brandishing a weapon of any sorts. Without the shooter saying anything all i can think is premeditated murder. If he had yelled, "Stop or I'll shoot" it would be a different story, but he just opens up. He should get the death penalty. If he was being bullied he should have had a taser, not a handgun.
No one needs to say “Stop or I’ll Shoot”. As long as you think you are going to be harm then it will be self-defense. Problem with this is he taped the killing. That IMO is a very bad idea even if you think it will be in your favor. What he should have done is not tape it and use his word and a good lawyer to get him out of the mess, which I think he has a very high probability of getting off. Just remember dead man don’t talk to the jury.