I actually have no problem with shooting a fleeing violent armed perpetrator. He is not just fleeing from his current crime, he is fleeing to his next crime where his victim(s) might not fare as well.
Right, so while it may not be legal to shoot a fleeing criminal on the grounds that the criminal is in flight, it may be perfectly legal to shooting a fleeing criminal you feel is endangering the public.
In the Jerome Ersland case, this did come up specificially and the DA discussed the matter and noted that Ersland, in his shooting pursuit of the fleeing armed robber (who stole nothing and who never fired a shot) was n his rights to do so. The robber was an obvious danger to the public.
Of course, then getting a gun and pumping several rounds into the unconscious robber on the floor is where Ersland screwed up, but until that time, according to the DA, the video indicated nothing illegal on the part of Ersland.
From the story in the OP, I have a feeling that the pharmacist was not protecting the public. He was chasing and shooting the robber out of "contempt of victim" which would be a lot like "contempt of cop" where cops go overboard for transgressions against them.