NORTH PHILADELPHIA (WPVI) -- Family members say the 18-year-old man who was shot and killed in North Philadelphia was defending his sister during a fight.Moses McMillan died after the shooting around midnight on the 1900 block of North Croskey Street.The incident began as a fight between McMillan's sister and a group of teenage girls.McMillan's mother says the entire incident happened right in front of the McMillan home.A number of neighbors tell police that the teenagers, mostly girls, were involved in some kind of ruckus in the middle of the block. But then they heard gunfire."Three shots. I heard three loud shots. My kids started screaming like, 'Daddy, what's going on?' I run back to the door and I see the kids running, laughing like it was a joke," one neighbor said.Police say Moses McMillan succumbed to wounds of the chest and abdomen.McMillan's mother says her son was mortally wounded as he was defending his sister from a gang of girls in an on-going dispute.The all-female bunch had been at the house earlier, then returned with at least one male who was wielding a handgun, and who police believe was the triggerman.Police are asking anyone who can help them catch the killer to call investigators right away.As with all homicides, a $20,000 reward has been posted by the City of Philadelphia.