A two-year-old boy has been been mauled to death after falling into the African painted dog enclosure at Pittsburgh Zoo.
The boy was visiting the zoo with his 34-year-old mother, who had stood him up on the railings so he could get a better view of the dogs.
He slipped and fell 14ft into the enclosure, where he was pounced upon by a pack of 11 dogs.
Describing the incident as "horrific", Pittsburgh police major crimes Lt, Kevin Kraus, told the Post Gazette: "He lost his balance, fell down off the railing into the actual pit and he was immediately attacked by 11 dogs."
Zoo president Barbara Baker gave a press conference about the fatality, the first ever at Pittsburg, saying: "The keepers did everything they could do, they responded immediately and were able to get several of the dogs into the back-up building."
Vets tried to use tranquillisers darts to get the dogs away, but one particularly aggressive one would not the leave the child alone, and police were forced to shoot it dead.
Pittsburgh Zoo: AP
Ms Baker has confirmed a medical examiner ruled that the boy was killed by the animals and not by the fall, telling NBC News: "What we understand from the medical examiner's report, the child did not die from the fall. The child was mauled by the dogs."
Onlooker Angela Cinti, told the 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."
She said she could see the little boy's lifeless body lying on the hill in the exhibit below, adding: "There were three dogs: one at his head, one on the left side of his neck and another one down by his leg. ... A [zoo employee] got there and hopped over a fence with a rake and he was banging ... trying to distract the dogs but they wouldn't move."
African painted dogs are an endangered species that are as big as medium-sized domestic dogs, the zoo said.
In the wild, they are only found in Africa, especially in savannas and lightly wooded areas. They are also known as the African hunting dog or Cape hunting dog.
The dogs hunt in packs, usually living off impala, gazelle, springbok, and wildebeest calves, although they have been known to kill and eat zebras, warthogs, and even ostriches.
The dogs' technique of disembowelling their prey has earned them a ferocious reputation.
According to the Daily Telegraph, Ms Baker said the zoo will carry out an internal investigation, and decision has not yet been made about the future of the exhibit.
World's deadliest animals
Boy, 2, mauled to death by wild dogs after falling into enclosure at Pittsburgh Zoo
Although they might look cumbersome and cute, hippos are actually one of the most feared animals in Africa, and can outrun a human. When a male feels its territory is threatened, or a female thinks her offspring her in danger, these animals can be particularly dangerous. And with huge teeth and mouth that can open four feet wide, it's a good idea to steer clear. Kills: An estimated 100-150 people a year. Deadly technique: Hippos will charge, trample and gore its victims, and have been known to upturn boats and canoes without warning. Lives in: Africa
Many people might not realise that the cape buffalo is one of the most dangerous animals in Africa, and will react with force when it feels threatened. These beasts can weigh up to 1.5 tons and stand at 1.7 metres high; they're so intimidating that even lions don't usually consider them dinner. Cape buffalos will charge, and then gore its victim to death with its impressive horns. Kills: An estimated 200 people a year. Deadly technique: These animals will charge and gore their victims to death with their huge horns. Lives in: Africa
Out of the world's 2,000 species of snake, around 250 are thought to be capable of killing a man. The Asian cobra does not have the deadliest venom, but is believed to be responsible for the biggest portion of the thousands of snakebite deaths every year. In Africa, the black mamba is the largest venomous snake and, during an attack, can strike up to 12 times, each time delivering enough neuro and cardio-toxic venom to kill a dozen men within 1 hour. Kills: An estimated 50-125,000 people a year. Deadly technique: A snake will use its fangs to pierce the skin and inject its paralysing venom. Lives in: Africa, Asia, Australia, North America
Box jellyfish can have up to 60 tentacles as long as 15 feet. And each tentacle contains enough venom to kill 50 humans, making it one of the most venomous marine creatures in the world. If stung, a box jellyfish can kill a man within minutes. Kills: An estimated 100 people a year. Deadly technique: Jellyfish use their tentacles to pump venom and paralyse its prey. Deaths in humans are usually a result of cardiac arrest. Lives in: Northern Australia, Papua New Guinea, Malaysia, Indonesia, the Philippines, Thailand and Vietnam.
Apart from humans, the mosquito is the deadliest creature on the planet. It kills millions of people every year through the spread of diseases like malaria, yellow fever, and dengue fever. Many of the malaria victims are children under the age of five. Kills: Two to three million people a year. Deadly technique: Female mosquitos pierce the skin with serrated mouth parts, and inject a saliva with a thinning agent to liquidise the blood. Lives in: Worldwide, more harmful in Africa, Asia and North America
The great white shark, which can grow up to six metres in length and weigh up to five tons, seems to have the most ferocious reputation. But, while they have been known to attack humans, most of these incidents are thought to be 'test bites', where the animal is deciphering whether he wants to eat you. And, generally, they humans are not on the menu. It is thought the aggressive bull shark is responsible for the most attacks on people. Out of the 360 shark species, only four are known killers: the great white, the bull, tiger, and the oceanic white tip. Kills: An estimated 100 people a year. Deadly technique: Sharks use their razor-sharp teeth to rip chunks out of its victims. Great whites usually take a big single bite, drag their victims into deeper waters, and wait until the prey bleeds to death before they eat it. Lives in: Florida, Australia, Hawaii and South Africa.
The are lots of different species of bear, but the polar, black and grizzly are the deadliest. Native to the Arctic, polar bears could decapitate a human being with one swipe of their massive paws. Bears generally attack when they are hungry, so it's a good idea to keep food away from your camp. Kills: An estimated 5 to 10 people a year. Deadly technique: Bear will use their teeth and claws to maul and trample their victims. Lives in: North America, Canada, North Pole, and Russia.
Crocodiles have been around for 200 million years, and are fearsome predators. The saltwater crocodile, or saltie, is the largest living reptile in the world, and can grow up to 21ft long and weigh 1.6 tons. These animals can run extremely fast on land, and, in the water, can swim as fast as dolphin. Many fatalities occur when people are washing or gathering food near river banks. Kills: An estimated 600-800 people a year. Deadly technique: Crocodiles will grab their victims with terrifying speed, and often launch into a 'death roll', weakening its prey, dragging it under water and drowning the victim. Lives in: Africa and Australia
Out of the 1,500 species of scorpion, the African spitting scorpion is thought to be the most deadly, and can spray its venom up to a metre. Arounf 25 species of scorpion are thought to be deadly to humans. Kills: An estimated 800-2,000 people a year. Deadly technique: Scorpions use their tail stingers to paralyse their prey with venom. Lives in: Worldwide; particularly Africa, the Americas and Central Asia.
Weighing in at up to eight tons, although beautiful creatures, elephants can be lethal. African elephants in particular can be aggressive, especially older bulls and young males. These creatures, unsurprisingly, are more aggressive in areas where poaching is rife or when their habitat is threatened. Kills: An estimated 300-500 people a year. Deadly technique: Most human deaths are result of the elephant trampling on its victim. Lives in: Africa and India
African lions are the biggest of the big cats, and are known to kill around 70 people in Tanzania alone every year. With the destruction of their habitat, human attacks by leopards in India, and the North American mountain lion are thought to be on the increase. Kills: An estimated 800 people a year. Deadly technique: African lions will often use strangulation to kill their prey, while tigers will attack from the back and aim for the jugular, and mountain lions will maul their victims. Lives in: Africa, North America, and India