This photo taken Sunday, Nov. 4, 2012 shows the exterior view of the front entrance of 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. 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. (AP Photo/John Heller)

A teddy bear rests at the base of a sign near the entrance to the parking lots for the Pittsburgh Zoo and PPG Aquarium on Monday.

A teddy bear rests at the post of a sign near the entrance to the parking lots for the Pittsburgh Zoo and PPG Aquarium on Monday, Nov. 5, 2012, in Pittsburgh. (AP Photo/Keith Srakocic)

An African Painted Dog yawns at the Pittsburgh Zoo and Aquarium in Pittsburgh as he lays in a pile of hay Thursday, March 12, 2009. (AP Photo/Gene J. Puskar)

The overlook platform where a boy fell into the exhibit that was home to a pack of African painted dogs is seen at the Pittsburgh Zoo and PPG Aquarium on Monday, Nov. 5, 2012, in Pittsburgh. (AP Photo/Keith Srakocic)

A sign to inform visitors about African Painted Dogs is seen in an observation area during a press tour that overlooks the enclosure where a boy fell into the exhibit that was home to a pack of African painted dogs at the Pittsburgh Zoo and PPG Aquarium on Monday, Nov. 5, 2012, in Pittsburgh. (AP Photo/Keith Srakocic)

The overlook platform where a boy fell into the exhibit that was home to a pack of African painted dogs is seen through a window from another observation area at the Pittsburgh Zoo and PPG Aquarium on Monday, Nov. 5, 2012, in Pittsburgh. (AP Photo/Keith Srakocic)

Barbara Baker, CEO and president of the Pittsburgh Zoo and PPG Aquarium, gestures to indicate the slope of a railing that is in the observation area of the African Painted Dog exhibit during a news conference on Monday, Nov. 5, 2012, in Pittsburgh. (AP Photo/Keith Srakocic)