I would say it's self defense, but if your going to hit someone in a situation like that, why hit them in the head??? Oh I remember now...that's how it's done in Hollywood. The one punch knockout. Because they hit they guy in the head and he died, they will pay for it. Now one good punch to the gut, slight upward thrust into the diaphram, the guys down. No visible marks. No damage. No one goes to jail.