CINCINNATI -- The killing of a gorilla at the Cincinnati Zoo in order to save a child who fell in its enclosure has sparked nationwide outrage.

Animal activists have created online petitions and Facebook pages after a special zoo response team shot and killed the 17-year-old gorilla named Harambe.

The 3-year-old boy (who was initially reported to be 4 years old) spent a terrifying 10 to 15 minutes alone on Saturday with the adult male gorilla. Harambe grabbed and dragged the little boy after the boy fell into the gorilla exhibit, officials said.

Many are angry the endangered gorilla was put down. Others want the boy's mother to face child endangerment charges, CBS News' Jamie Yuccas reported.

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Facebook pages like "Justice for Harambe" are quickly spreading. The Facebook page currently has more than 11,000 likes.

Facebook page set up to petition Harambe's death at the Cincinnati Zoo. CBS News

A petition on Change.org asks for new legislation to be passed to protect animals like Harambe. The petition has garnered nearly 4,000 signatures so far.

"In light of the recent tragedy at the Cincinnati Zoo in the death of Western Lowland Gorilla Harambe and the enormous loss of this CRITICALLY ENDANGERED animal, we would like to pass Harambe's Law, so there are legal consequences when an endangered animal is harmed or killed due to the negligence of visitors," the petition reads.

Zoo Director Thane Maynard said the zoo's dangerous animal response team decided the boy was in "a life-threatening situation" and that they needed to put down the 400-pound-plus male gorilla.

The boy's family said in a statement Sunday that the he was home and doing fine.

"We extend our heartfelt thanks for the quick action by the Cincinnati Zoo staff. We know that this was a very difficult decision for them, and that they are grieving the loss of their gorilla," the family said.

Animal rights group People for the Ethical Treatment of Animals (PETA) said the zoo should have had a second barrier around the exhibit.

"Even under the 'best' circumstances, captivity is never acceptable for gorillas or other primates, and in cases like this, it's even deadly," PETA said.

Zoo officials said the boy fell after he climbed through a public barrier at the Gorilla World exhibit Saturday afternoon. He was picked up out of the moat and dragged by the gorilla for about 10 to 15 minutes, according to a Cincinatti Fire Department press release.

Harambe the gorilla is seen alongside the little boy who fell into the enclosure at the Cincinatti Zoo. CBS News

Authorities said the child, who has not been identified, fell 10 to 12 feet. He was taken to Cincinnati Children's Hospital Medical Center, and he was released later Saturday evening. Fire department officials described his initial injuries as "serious."

"They made a tough choice and they made the right choice because they saved that little boy's life," Maynard said. "It could have been very bad."

But he mourned the loss of the gorilla, which came to Cincinnati in 2015 from the Gladys Porter Zoo in Brownsville, Texas.

"We are all devastated that this tragic accident resulted in the death of a critically endangered gorilla," he said in a news release. "This is a huge loss for the zoo family and the gorilla population worldwide."

Panicked zoo visitors watched helplessly and shouted, "Stay calm!" while one woman yelled, "Mommy loves you!" as the gorilla loomed over the boy.

The boy sat still in the water, looking up at the gorilla as the animal touched the child's hand and back. At one point, it looked as though the gorilla helped the youngster stand up.

Two witnesses said they thought the gorilla was trying to protect the boy at first before getting spooked by the screams of onlookers. The animal then picked the child up out of the moat and dragged him to another spot inside the exhibit, zoo officials said.

Gorilla picks up the boy and begins to drag him at the Cincinatti Zoo. CBS News

Witness Kim O'Connor said she heard the boy say he wanted to get in the water with the gorillas. She said the boy's mother was with several other young children.

"The mother's like, 'No, you're not. No, you're not,'" O'Connor told WLWT-TV.

Another woman said that just before the boy fell, she saw him in bushes beyond a fence around the exhibit.

"I tried to grab for him. I started yelling at him to come back," Brittany Nicely told The Cincinnati Enquirer. "Everybody started screaming and going crazy. It happened so fast."

Zoo staff cleared the area and visitors heard gunfire a few minutes later. Firefighters then rushed into the enclosure and picked up the boy.

Lt. Steve Saunders, a Cincinnati police spokesman, said there are no plans to charge the parents.

Two female gorillas also were in the enclosure when the boy fell in but zoo officials said only the male remained with the child.

"The safety of our visitors and our animals is our #1 priority," said Maynard later. "The barrier that we have in place has been effective for 38 years. Nevertheless, we will study this incident as we work toward continuous improvement for the safety of our visitors and animals."

Maynard said the gorilla didn't appear to be attacking the child, but he said it was "an extremely strong" animal in an agitated situation. He said tranquilizing the gorilla wouldn't have knocked it out immediately, leaving the boy in danger.

It was the first time that the team had killed a zoo animal in such an emergency situation, Maynard said. He called it "a very sad day" at the zoo.

The area around the gorilla exhibit was closed off Saturday afternoon as zoo visitors reported hearing screaming.

Maynard said the zoo believes the exhibit remains safe.

Visitors left flowers at a gorilla statue Sunday. Gorilla World remained closed, but the rest of the zoo was open.

The zoo prides itself for its work in protecting endangered species, and has been part of successful captive breeding efforts in recent years in the effort to save the endangered Sumatran rhino.