(CNN) The mother of a child who fell into the gorilla enclosure at the Cincinnati Zoo last weekend spoke in a steady voice to keep her son calm. But she couldn't contain her fear when the 450-pound Harambe violently pulled the boy away, according to a copy of the call obtained by CNN on Wednesday.

"He's dragging my son! I can't watch this," she told the 911 operator. "I cannot. I can't watch."

The mom had called 911, calculating it was the quickest route to alerting zoo authorities to rescue her 3-year-old son.

"Hi. My son fell in the zoo at the gorillas," the mom says on the call, her voice frantic but steady. "The Cincinnati Zoo, my son fell in with the gorilla. There's a male gorilla standing over him. I need someone to contact the zoo please."

The 911 operator informs her help is on the way -- another spectator at the zoo had also called. The mother can be heard calling down to the boy -- "be calm, be calm! be calm, be calm" -- apparently as Harambe, a silverback gorilla, stands the boy up, looks him over and tugs up his pants.

Then the fear heightens in her voice as Harambe drags the boy through the water in the moat. The call cuts off 49 seconds after it started, as Harambe drags the boy briefly out of sight.

"I need to call my dad," she tells the operator.

'Help is coming'

Deidre Lykins said she saw the boy while he was in the gorilla's enclosure, but she did not see how he got there.

"I hear (the boy's mother) calling in the background, 'where's my son, where's my son!' " Lykins told CNN's Anderson Cooper.

When she found out he was in the gorilla's enclosure, she panicked.

"She covered her face and started screaming, 'that's my baby, that's my baby!' " Lykins said.

"My husband is talking to the child, saying 'just stay right there buddy, it's OK, it's OK, help is coming. ' "

She said the gorilla dragged the child violently as the boy alternated between crying and not crying.

"If you had seen the gorilla dragging this baby with his little precious face ... just bouncing off the rocks, he just looked lifeless," she said. "We did not leave the zoo until we knew that the little boy was OK."

In a statement Wednesday, the family said the boy had a checkup with his doctor and "is still doing well."

The unidentified boy was not seriously injured after his Saturday encounter with Harambe, an endangered western lowland gorilla. After 10 minutes, zoo personnel shot and killed the animal.

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"We continue to praise God for His grace and mercy, and to be thankful to the Cincinnati Zoo for their actions taken to protect our child," the boy's family said.

"We are also very appreciative for the expressions of concern and support that have been sent to us. Some have offered money to the family, which we do not want and will not accept. If anyone wishes to make a gift, we recommend a donation to the Cincinnati Zoo in Harambe's name."

The zoo has performed a necropsy on the gorilla but has not released the results.

A research doctor extracted and froze the gorilla's genetic material after his death, the zoo said.

Review aimed at parents

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Cincinnati police said Tuesday they are reviewing the incident with a focus on the actions of the boy's parents and family. It is not related to the operation or safety of the Cincinnati Zoo, authorities said.

"After the review, we will determine if charges need to be brought forward," police spokeswoman Tiffaney Hardy said.

"If it is determined charges need to be brought forward, we would then discuss it with the Hamilton County prosecutor's office." The prosecutor's office declined to say how long the investigation might take.

Authorities have said the boy's mother was with the child when he slipped past a fence and tumbled into the moat.

The parents are cooperating with police and are still evaluating whether they will seek legal representation, family spokeswoman Gail Myers said.

Critics united in grief

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Harambe's name is Swahili for come together in unity for a common cause. And critics have rallied together against the gorilla's killing.

Uproar and vitriol has poured in, especially on social media against the boy's mother after zoo officials killed the western lowland silverback to protect the boy.

"This beautiful gorilla lost his life because the boy's parents did not keep a closer watch on the child," the petition states.

Kimberly Ann Perkins O'Connor, who saw the incident, said the boy told his mother he was going to get into the moat. The mother told her son to behave before she became distracted by other children with her, O'Connor said.

"The little boy himself had already been talking about wanting to go in, go in, get in the water and his mother is like, 'No you're not, no you're not,' " O'Connor said. "Her attention was drawn away for seconds, maybe a minute, and then he was up and in before you knew it."

'The child is safe'

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Thane Maynard, the zoo's director, has firmly stood by the decision to kill the gorilla.

"We are all devastated that this tragic accident resulted in the death of a critically endangered gorilla," Maynard said.

However, he said, those second-guessing the call don't understand the animal.

"That child's life was in danger. People who question that don't understand you can't take a risk with a silverback gorilla -- this is a dangerous animal," he said. "Looking back, we'd make the same decision. The child is safe."

Famed primatologist Jane Goodall's response to the killing highlighted the conflicted nature of the decision to kill the animal.

"I feel so sorry for you, having to try to defend something which you may well disapprove of," Goodall wrote in an email to Maynard.

Goodall described the killing as "a devastating loss to the zoo, and to the gorillas."

More investigations

The Association of Zoos and Aquariums, which accredits zoos, announced it is investigating the incident.

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"We'll of course be ... working with Cincinnati to figure out what happened and make sure we can firm that up so it doesn't happen again," spokesman Rob Vernon said.

The U.S. Department of Agriculture, which inspects the zoo annually, said it will determine whether the facility was in compliance with the Animal Welfare Act, a federal law that monitors the treatment of animals in research and exhibition.

If not, a formal investigation would be warranted, USDA spokeswoman Tanya Espinosa said.

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CNN independently reviewed USDA records for the past three years, which are all that the agency maintains. It found nine instances in which the zoo was out of compliance. None involved the gorilla exhibit.

Two involving veterinary care were directly tied to the health or wellness of the animals, and seven dealt with other issues.

All were resolved, according to USDA reports.

Animal rights group steps in

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An animal rights group has requested an investigation by the USDA.

Stop Animal Exploitation Now alleges the zoo violated the Animal Welfare Act, according to a letter by Executive Director Michael A. Budkie.

The letter cites USDA inspection reports dated November 2014 and March.

The November 6, 2014, report cites a door to an outdoor monkey enclosure had multiple wooden boards in disrepair. It also detailed deterioration in a horse enclosure.

The March report documented an incident in which two polar bears got into a service hallway accessible only to zookeepers. The dangerous animal response team quickly secured the area and used tranquillizer darts to subdue the bears.

Separately, Maynard, the Cincinnati Zoo director, noted a zookeeper lost her arm in a 1990 incident but didn't go into further detail.

CORRECTION: An earlier version of this article incorrectly described an incident when a Cincinnati zookeeper lost her arm. That incident occurred in 1990.