The duel where he was shot (one of them) was strategic. The man he was fighting insulted his wife. Andy Jackson married a divorced woman, which many people still considered adultery. Jackson wanted to kill the man so he allowed him to fire first, so that he had all the time he needed to line up his shot. After killing his opponent, his doctor told him he could not believe he was still standing after being shot. Jackson replied that he could have been shot in the head and still would have killed him.
u/Breacherbear/ provided more details in another forum: