Badges
Never!!! Bad Idea. If you are a cop carry a badge. Anybody else is asking for trouble. I am not going to pretend to be a cop.
I will only draw my gun If it is the absolute last resort and I anticipate firing it. If I have to draw my weapon, fire it and the BG is still alive , I would disarm him( if at all possible) and re-holster while waiting for LE. I realize that use of force situations are dynamic and unique. If I felt there were more threats, and I had my weapon still drawn when LE showed up , I would drop my gun as soon as I saw the LE put my hands in the air and wait for instructions.
I would instruct whomever is calling 911 to give a detailed description of me (the good guy) and the bleeding guy on the floor (the bad guy).