As investigators continued to probe the horrific death of a two-year-old Pittsburgh Zoo patron who fell into the African painted dog enclosure yesterday morning, it remains unclear if the boy died as a result of the fall or the subsequent mauling.

The unidentified toddler apparently lost his balance after being placed on the enclosure's four-foot wooden railing by his mother, and bounced off a mesh net meant to prevent objects from falling into the exhibit.

Immediately, all eleven wild dogs attacked the boy, as his mother screamed for help.

Staff members successfully lured seven dogs away from the boy's body, but four refused to budge. They attempted to scare them away with "dummy tranquilizer rounds," but "the dogs were in pack mentality and not responding," according to Major Crimes Lt. Kevin Kraus.

Police officers were ultimately forced to put down one of the dogs who remained aggressive and would not back away.

The entire ordeal lasted twelve minutes, at the conclusion of which the child was pronounced dead.

The zoo's African painted dogs exhibit opened six years ago after the pups were born. Since then, there has been only one notable incident involving the endangered animals wherein the dogs managed to infiltrate a separate section of the exhibit by crawling under a fence, forcing a temporary lockdown of the entire zoo.

"They are one of the most aggressive predatory animals in the wild," Columbus Zoo director emeritus Jack Hanna told ABC News. "A zookeeper, a tranquilizer gun could not have helped."

This is believed to be the first death of a child at an accredited zoo in over 40 years.

UPDATE: And it's a sad one: It seems the boy — identified as Maddox Derkosh — did perish as a result of the mauling rather than the fall. "What we understand from the medical examiner's report, the child did not die from the fall," said Pittsburgh Zoo president Barbara Baker. "The child was mauled by the dogs."

Baker apologized to Maddox's parents, Elizabeth and Jason Derkosh, and called the tragic accident "your worst nightmare as a zoo professional."

[photo via Shutterstock]