It is laughable how Americans who are on the same side for killing prisoners say opposite things about their police killing unarmed Blacks and getting off.
The difference is that the prisoner broke the law, and the penalty for certain murders is death. When a police officer kills an unarmed black, it's because he believed there was a threat of some kind, and later proven true through investigations and a grand jury in many cases.
It's not just police that can kill an unarmed attacker. As a CCW holder in my state, I have the same right. There is no law on the books that state you can only use deadly force when the opponent has a weapon. Let me give you an example:
Let's say I'm in my car and another driver gets pissed at something I did, then comes out and tries to get me out of my car by busting my window and pulling me out, I have the legal right at that point to use deadly force. That's our law. Or I see an elderly man get jumped by three younger stronger guys and they start beating the living hell out of him, as an armed citizen, I have the legal right to use deadly force to stop the attack. The cops can't even write me a ticket. They may take my gun for a short period of time, but by law, they have to return it to me in the same shape they took it from me.