A two-year-old boy was mauled to death Sunday, by a pack of African painted dogs in a Pittsburgh zoo.

The child, who was visiting the Pittsburgh Zoo & PPG Aquarium with his mother, fell about 11 feet off a wooden railing on which he was standing to look at the animals. The boy reportedly lost his balance and fell into an enclosure where a pack of African painted dogs were on display, zoo officials said.

As soon as he fell, a group of 11 dogs started attacking him resulting in his death. The incident is said to have taken place at 11:48 a.m. Sunday.

"The screams just kept coming and coming: 'Someone help. Someone has to do something'," Angela Cinti, of Bethel Park who was visiting the zoo with her boyfriend, told the Pittsburgh Post-Gazette.

However it is still not clear whether the boy died from the fall or after being attacked by the dogs, Zoo President and Chief Executive Officer Barbara Baker said at a news conference. "It's clear that the dogs did attack the child, but whether he died of the attack or the fall has yet to be determined," Baker said.

Immediately after the incident, the zoo visitors were moved inside the nearest buildings and held there for about half an hour. Pittsburgh police Major Crimes Lt. Kevin Kraus said that zoo staff rushed to the dogs' enclosure. 

The zoo keepers used "dummy tranquilizer rounds," to allure the dogs away from the child.

One of the dogs, which did not leave the child and acted aggressively towards the zoo keepers, was shot dead by a police officer. The child was declared dead around 12 p.m. Neither his name nor his mother's name was revealed by the authorities. But they said that she was a 34-year-old lady from Pleasant Hills outside Pittsburgh, according to a report from NBC News.

The zoo was closed for the day. Police officials are investigating the incident.