Maybe its different in America,...
It is,
quite different in America.
While shooting someone running away in the back is generally not justified, or moral, there are specific circumstances where the recognizes it as justifiable, by POLICE officers but not for regular citizens.
This case is borderline what the law envisioned, when police are justified shooting someone fleeing, in the back. However, our information at this time lacks some key points that would clearly justify the shooting.
Consider, had the suspect been SHOOTING, either at the officers, or anyone else, while fleeing, shooting them in the back (or anywhere else) would easily be justified. Virtually automatic approval. Safety of the public at large, etc. Even though running away from the police, they are running toward someone else. A "clear and present danger" etc.
Our legal system here would likely approve of a civilian doing the same, IF that civilian could see others in immediate danger. But if there was no one else in sight, there would not be an immediate threat to others, and if that is not present, then the law considers stopping the fleeing subject to be the responsibility of the police, and not the private citizen. It's kind of twisted logic, but its what we have.
In the case under discussion here, there was no shooting by the fleeing subject. It is currently under investigation whether the subject pointed the "gun" at the officer, or the officer just thought he did. The video released does not seem to support that he did. At this time... (unaltered) pictures don't "lie", but they CAN be misinterpreted. And, the segments shown to the public might not be all the information pertinent.
We have the rest of recorded history to discuss and decide what that officer had to decide in a couple of seconds. How this matter proceeds through both the legal system and the court of public opinion is something to be observed and studied as an example of what should be, and should not be done. It may result in a change of police policy or even a change in the law, or it may not. Too early to know, either way.
I remember, decades ago, a weeks long manhunt for a suspected multiple murderer. He had been seen several time, by the police, but they had been unable to physically catch him. He was seen to be armed, with a rifle, but never pointed it at the police or fired at them. Under the rules of the day, those police were not allowed to shoot him, if he didn't shoot, or try to shoot them. He was finally caught, after being shot by a Game Warden, who was not legally bound to follow police policy about shooting armed suspects.
In that place, the policy for the police was changed, not a long after.
to wrap up the story, he stood trial, and was convicted of brutally killing 3 teenage campers. He went to prison, for life. A couple years later, he escaped. "Everyone" went looking for him, and his body was found a couple days later in some woods. "Shot multiple times by at least 3 different guns, by a person or persons unknown" was how one newspaper reported it. The police never found any suspects....