It allows you to say later, “I only meant to shoot him in the kneecap! But I was so upset that my aim must have been off. And that is how he took five to the torso and as he was falling that must have been when he took two to the head. That is what must have happened officer!”
Second mistake - talking to the cops after a shooting. That is what lawyers are for. In most states if you are justified in shooting you are justified to kill.