I was reading a book by Peter Hathaway Capstick the other night and he mentioned an event where a fellow PH told him of accidentally killing an elephant with a .22LR. The friend took Pete out into the bush and proved it by doing it again. With a broadside shot, the shooter waited 'till the elephant stepped forward and then shot into the chest immediately behind the front leg. The skin is thin and soft at this point and the bullet pierced the heart and the elephant collapsed within a minute.
Placement and penetration.