PITTSBURGH » A 2-year-old boy who fell into an exhibit of African wild dogs was killed by the animals, not the fall, the president of the Pittsburgh Zoo said today, adding a horrific coda to a tragedy that has devastated staff and shocked patrons.

The boy’s mother had picked him up and put him on top of a railing at the edge of a viewing deck late Sunday morning when he lost his balance and fell, said Barbara Baker, CEO and president of the Pittsburgh Zoo and PPG Aquarium. There was a safety net below the railing, but it failed to catch him and the boy dropped more than 10 feet into the enclosure, she said.

“The child was so small that he bounced. He bounced twice and then he bounced into the exhibit,” said Baker, tearing up at a news conference this afternoon.

The animals attacked the child so violently and quickly that by the time a veterinarian and other zoo staffers arrived seconds later, they determined it would have been futile to try rescuing the boy, she said.

Baker said she had been informed by the Allegheny County medical examiner that an autopsy determined the boy survived the plunge. The medical examiner’s office has not yet publicly confirmed its findings or released the boy’s name.

The African painted dogs are about as big as medium-sized domestic dogs, about 37 to 80 pounds, according to the zoo. They have large, rounded ears and dark brown circles around their eyes and are considered endangered.

The attack happened in a 1.5-acre exhibit called the Painted Dog Bush Camp that’s part of a larger open area where elephants, lions and other animals can be seen. Visitors walk onto a deck that is glassed on the sides, but open in front where the roughly four-foot railing is located.

The zoo was immediately closed after the accident but was expected to reopen Tuesday.