Witnesses describe a horribly heartbreaking scene Sunday at the Pittsburgh Zoo & PPG Aquarium after a 2-year-old boy fell into an exhibit housing wild African dogs.

"The screams just kept coming and coming," Angela Cinti, 20, tells the Pittsburth Post-Gazette. "We were on our way to the polar bear exhibit when we heard the most horrible piercing screams. ... Someone was begging for help, asking someone to do something."

The little boy, who has not been identified, died. According to The Associated Press, it's possible he was killed by the fall — which measured somewhere between 11 and 14 feet.

But Barbara Baker, president of the zoo, told reporters Sunday that the child died from a mauling by the 11 dogs in the enclosure. The Post-Gazette has video of Baker's comments and one witness's account of what happened.

Pittsburgh's TribLive adds these details about how the tragedy happened:

" 'The mother picked the child up, put him on the railing,' Major Crimes Lt. Kevin Kraus said, describing the moments before the 11:45 a.m. attack. 'Almost immediately after that, he lost his balance and fell into the pit.'"Barbara Baker, zoo president and CEO, said the 11 dogs in the exhibit, which are territorial by nature, went into a pack mentality and attacked the boy when he hit the ground."

The AP reports that "authorities said that zoo staff and then police responded 'within minutes' but visitors described that time as being filled with screams for help. Zookeepers called off some of the dogs, and seven of them immediately went to a back building. Three more eventually were drawn away from the child, but the last dog was aggressive and police had to shoot the animal."

It appears that no bystanders risked the jump into the exhibit.

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