Defensive shooting is not same as police shootings, not even close, there is little chance for follow up shots, every shot will be looked by a DA as a reason to throw more charges, for each shot there will be a separate charge, the more you shoot the more chances you hit someone else, unlike police, citizens do not have QI, you will be held accountable for every shot, even if you are justified shooting a threat you will still be charged if a bullet that came out of the bad guy hit unintended target, even if it hits a car someone was in, not the person. you will be charged for that, and be sure jury will find you guilty for that shot regardless of intent and situation, so you definitely need to worry about overpenetration, and number of shots you fired.