That is pure speculation as nobody genuinely knows the robber's subsequent plans.
We now know the robber had murdered a person before, so he was unpredictable.
This is not the point, and an extremely dangerous one to take in the realm of using deadly force. Unless one's life goal is to end up with a free ride in the prison system, that is.
You make the decision to use, or not to use, deadly force on the EXISTING circumstances as you know them to be AT THAT TIME. To use deadly force simply because "nobody genuinely knows the robber's subsequent plans" is the height of folly. You make that decision based on the totality of the existing circumstances which, mind you, are going to be judged by others after the fact under the "reasonable person" standard.
This isn't just a case of shooting someone who had their back turned and was leaving. I conceded in my prior post that it might indeed be possible to successfully endure a trial if that were all it was.
But it was not.
The biggest problem with this shooting is what happened AFTER the first four shots.
The bad guy went face down HARD and STAYED that way. Then the patron approached and not only shot him four more times in the back, but paused, did some additional assessment on a face-down, unmoving person, and shot him again.
Knowing more about the bad guy's history after the fact has absolutely NO BEARING on the actions that took place in this shooting.
The fact that the bad guy might be judged "unpredictable" in light of such knowledge likewise has absolutely NO BEARING in this case. You and I can look at each other and say the same thing simply because we don't know each other.