He did more just run from a cop. He fought a cop and grabbed his taser. This is what set the shooting in motion, not just running from him.
If this chain of events had gone down between the deceased and a private citizen (say, you or I), we’d be looking at a murder-2 charge every time. It is well established that a “coup de grace” after the threat is ended in a self-defense situation is a crime.
A fleeing unarmed man being no threat in any serious sense of the word, the only real question before us in this case is whether a police officer is allowed to use deadly force as a means of apprehending a fleeing suspect.
Basic firearm instruction tells us that this is not the case. “Never point a gun at anything you do not intend to destroy” is the rule, any responsible weapons training makes this clear before the trainee ever gets to touch a weapon.
The job of the law enforcement officer is to apprehend suspects, not to destroy them. The reason that is so is that we at least pretend to have a justice system where a man is innocent until proven guilty and is allowed to present a defense of his actions before punishment is carried out against him.