You would be amazed at how many people own guns and don't know how to use them LOL Someone is scared, they go out buy a gun, never practice with it, and then if they need it, worse things can happen (particularly people who leave them laying around the house with children around).
That said, by the same token, you should not only know how to use one if you own one (as well as practice), but also know your laws about their use.
The example I was giving you looking for an answer from you is a classic reason why when you carry a firearm (if you're legally able to do so), you should know the law as well.
Per the situation I gave you, I mentioned that you just walked around the corner and saw what was taking place at that moment in time (man going to hit a woman). Fact is, you have no clue how those two came to be in their position when you came upon them. You shoot the man, and you find out later that it was actually the woman who was the aggressor and it was the man who thought he was defending his life, you're going to be in a world of trouble. You don't carry a weapon to play cop, you carry it to save YOUR life only or your immediate loved ones, and you know what the situation is from start to finish.
This isn't meant as a knock, but you're watching too much TV if you think you're going to hit someone in the arm and leg if that's where you're intentionally aiming at.