You decide to open the door. It is your partner, James. But before you could make sense of who it was, he yelled “BOO”. And out of instinct, you shoot James in the head. You get on your knees to check his pulse. James is dead.

You call 911, and tell the story. They ask you if you saw the killer. You reveal you did it out of instinct. You are incarcerated for shooting an unarmed man.
End Of Story