Comparison with police is a good point. If it were an unarmed Black man shot by police in the same scenario, how many nights of “peaceful protests” would be justified?From the perspective of legal, statutory justification for the use of deadly force in self-defense: is there a difference? No, I do not think that there is. Whatever imminent threat that might have existed (and that is a stretch, assuming that a face slap constitutes an imminent threat of death or great bodily harm) absolutely no longer exists when the would-be threat physically extricates himself from the confrontation (whether "retreating"or "creating distance").
And as for the spray: the shooter was the initial, physical aggressor, and unlawfully made physical contact with the victim. The use of spray in self-defense in that circumstance, thus, would have been legally justified. Ergo, at no time was the shooter legally justified in using deadly force against his victim.