"We are heartbroken about losing Harambe, but a child's life was in danger and a quick decision had to be made by our Dangerous Animal Response Team", Zoo Director Thane Maynard said in a statement Sunday.
The gorilla was said to be a critically endangered species.
Animal rights activists are reacting strongly on social media after a gorilla was killed at a Cincinnati zoo on Saturday.
Two female gorillas also were in the enclosure when the boy fell in but zoo officials said only the male remained with the child. There was already fire department personnel at the zoo because of a sick person, and they responded immediately to the pen, District Fire Chief Marc Monahan said. Tranquilizers may not have taken effect in time to save the boy while the dart might have agitated the animal, worsening the situation, Maynard said.
A blog post on the website for People for the Ethical Treatment of Animals questioned why it was necessary to kill the gorilla and whether zoos could meet the needs of such animals.
After the gorilla was shot with a rifle, the child was taken to Cincinnati Children's Hospital with non-life-threatening injuries, CNN affiliate WKRC reported.
The stunning footage conjured up memories from 1986 in a similar zoo incident.
Endangered gorilla killed after boy falls into zoo cage
Harembe's death comes just days after two lions were killed as they mauled a man who entered their pen at a Chilean zoo in an apparent suicide attempt.
A zoo official confirmed the incident during a press conference... and the Internet is now abuzz over who is to blame for this tragedy. And while zoo officials never wish to practice their training in a real-life scenario, human life is always the "first priority". The boy fell about 15 feet, landing in the enclosure where he was approached by Harambe, a 450 lb. male Western lowland silverback gorilla.
At one point a woman appearing to be the child's mother yells down, 'mommy's right here', 'mommy loves you', and then says 'Isaiah be calm', as the boy can be heard crying. "When they tell you don't climb and go, you have to pay attention because bad things can happen no fault of the animal". "You don't need an elephant in a cage to learn about elephants". Within the past year, the Ringling Bros. and Barnum & Bailey Circus announced it would retire its elephant act by 2018, and SeaWorld has agreed to end captive breeding of killer whales.
The Hashtag #RIPHarambe is trending on Twitter and more than 4500 had liked the Facebook page Justice for Harambe.
"It is believed that the situation was caused by parental negligence", it adds, before calling for "the parents to be held accountable for the lack of supervision and negligence that caused Harambe to lose his life".
Lt. Steve Saunders, a Cincinnati police spokesman, said there are no plans to charge the parents. Maynard said Lowland Gorillas are very endangered animals. "The kids, the zookeepers, the other gorillas that now don't have him there anymore".
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