The boy -- identified as Deon Williams -- was transported in serious condition to Comer Children's Hospital, but later pronounced dead, police said shortly before 5 p.m.
Preliminary reports from Chicago police indicate that the weapon accidentally discharged while two teens, including the victim, were playing with it.
Williams' sisters said the gun was brought into the house by a friend of their brother and it was the friend who was in possession of the gun when it discharged.
The incident occurred at about 3 p.m. in the 7300 block of South Aberdeen Street on the city's South Side.
No one was in custody.
Chicago police are investigating.