Can you imagine the carnage if normal civilians were allowed to shoot with as little repercussion as a cop? For most of us, a shooting would be judged on if a reasonable person would conclude he was, indeed, in danger of death or severe injury.
With cops, the standard seems to be, “Were voices raised? Was the cop stressed?”
There would be little or no difference. Normal civilians don't WANT to shoot people. That's the scary part.