I never accept the story line. What really happened is probably not what the reporter wrote. Most likely, the retired police officer fired at a time that was safer for him, such as when the robber turned or shifted his eyes somewhere else.
AND if you were carrying and saw a robbery in progress, you would be inclined to retrive your weapon and wait for the right opportunity, which killing the perp without anyone else being harmed proves was the ‘right moment’ to shoot. I practice tat a lot and I find it comforting to know that the reaction time of someone holding a weapon in the open but not in the act of shooting is longer than someone intent to shoot and shoot decisively.