In other threads here, some folks have said things like "anyone who attacks me will die" or that old favorite "dead men tell no tales."
Well, that's effectively what the victim did here. He made sure that perp died, by walking up to the prone and immobile perp and shooting him an additional 5 times. So, how's that working out for him? Not so well, I'd say.
Dead men may not tell any tales, but there will be witness that you don't see (in this case, video), and forensic evidence. You have to stop shooting after the threat is over. One extra bullet after that can turn a justifiable homicide into a murder one charge. This case is a prototypical example of that. The shot(s) fired in the initial encounter were legally justified; the extra 5 were not.
At best, the victim will spend his life savings defending himself. At worst, he'll die in jail.
Don't make the same mistake. Don't tell yourself "dead men tell no tales." Don't post it here. Don't say it to your friends. Don't even think it.
Your goal in a defensive shooting is to stop the attack. The perp may die as a result, but that is not what you are trying to achieve. Once the threat is over, stop shooting, take cover, and call the police. If the victim in this case had done that, he wouldn't be facing this horrible legal jeopardy.