The child fell into the exhibit and the African wild dogs pounced on him and mauled him, but police don't know whether the boy died from the 11-foot fall Sunday or from the attack.
Lt. Kevin Kraus of the Pittsburgh police described the accident as "horrific."
Authorities haven't released the names of the boy or his mother. She is 34-years old and lives just outside Pittsburgh. Police said the boy's father arrived soon after the accident.
African wild dogs are considered endangered.