The so-called painted dogs are about as big as medium-sized domestic dogs, and 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.
In May, some of the dogs crawled under a fence and escaped into a part of the exhibit that's usually closed. The zoo was on lockdown for about an hour as a precaution.
Past fatal attacks at have prompted zoos around the nation to review safety features of their exhibits. In 2007 a tiger jumped over a wall at the San Francisco zoo, killing one visitor and wounding two others. Authorities first said the wall was 18 feet high, but a review found it was just 12 ½ feet.
In September a man jumped off an elevated viewing train at the Bronx Zoo in New York and was severely mauled by tigers.
Kraus said there was nothing to prevent visitors to the painted dog exhibit from jumping into the exhibit area.
Police and the Allegheny County medical examiner's office are investigating, and they haven't yet interviewed the mother and father, who are receiving grief counseling.
Baker said the zoo, which has never had a visitor death, will also investigate. She said no decision has been made yet on the future of the exhibit.
Associated Press writer Ron Todt in Philadelphia contributed to this report.