Authorities have not charged the boy who fired the weapon Friday at the Crestbury Apartments on Hunter Street.
Camden County Prosecutor Warren Faulk says the wounded child was taken to a hospital and is expected to survive.
The investigation is focusing on how the children had access to the handgun and also probing whether the shooting was an accident or purposeful.
Prosecutor's Office spokesman Jason Laughlin says investigators have met with the boy who did the shooting and no charges have been filed. He says investigators want to speak with the boy who was shot, but that might not be possible for a few days.
No names have been released.