At least never talk to the cops without your lawyer present. In my CC class I was taught that once the bad guy was down and no longer a threat (use that language), put down your gun, ask others to stay as witnesses, and call 911. Tell them that the threat is under control. I would add that I would ask anyone with training and a gun to control the doors.
You are under no legal obligation to cooperate with the police. Moreover, if you do call 911, the cops will take your gun. It is better to just walk away.