I'll put on my instructor hat for a moment: That's not exactly correct. If, as a civilian in the US, you use a gun defensively, it should be to stop the threat. When the threat stops, stop shooting. Not before, and not after.

We train to aim for the center of mass, because that gives you the best chance to disable the attacker. Certainly, that can kill someone. But your intent should be to stop the threat.

As for legal issues, I'm not an attorney and this isn't legal advice. I strongly urge you to consult a competent attorney in your jurisdiction if you carry a gun as a civilian.