The 1985 SCOTUS ruling that narrowed the fleeing felon rule does not refer to “bystanders”. The word used is “others”, which would seem to include people not in the immediate vicinity. And the legal standard is not 20/20 hindsight but the officer’s reasonable judgement at the time. From what I’ve seen so far, I don’t think Slager had probable cause to believe that Scott posed a threat of serious physical harm to himself or others. But given the adrenaline of the moment and the fact that Scott had assaulted him and apparently taken his weapon, I’m not sure of that beyond a reasonable doubt. I just don’t think it’s as clear cut as you’re making it out to be.
It is exactly as clear cut as it appears. There was absolutely no danger posed by Walter Scott to anyone, much less the police officer, when he was shot 5 times in the back.