He was transported to Le Bonheur Children's Hospital in critical condition Thursday afternoon.
The victim's brother told police Sibley was playing with the weapon before the victim was shot, according to the affidavit. The brother said he hid in the closet and then heard the shot.
He also told police his father has played with guns before and pointed them at him and his brother. The victim's sister said Sibley called the police after the victim was shot and said his son had shot himself.
At the hospital, Sibley told police he had the gun in his hand when it fired and struck his son and he had transported his son to the hospital in his car.