A security guard closes the gate at the Pittsburgh Zoo, where zoo officials say a young boy was killed after he fell into the exhibit that was home to a pack of African painted dogs, who pounced on the boy and mauled him, Sunday, Nov. 4, 2012. It's not clear whether he died from the fall or the attack, said Barbara Baker, president and CEO of the Pittsburgh Zoo & PPG Aquarium.

PITTSBURGH - Police say a 2-year-old boy visiting the Pittsburgh zoo was killed when he fell off a railing that his mother had put him on top of it to view a pack of African painted dogs.

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.