Gorilla killing: 911 recording released of the moment mother at Cincinnati Zoo saw Harambe 'dragging' her son

'There's a male gorilla standing over him. I need someone to contact the zoo please,' the boy's mother tells the operator

A recording of the dramatic and heart-stopping moment the mother of a three-year-old boy called 911 after watching her son fall into the gorilla enclosure of a zoo in the US has been released.

Michelle Gregg, 32, dialled the emergency services to tell them to contact officials at Cincinnati Zoo while she remained at the enclosure to urge the boy to "keep calm".

She begins steadily, telling the operator in a steady tone: "Hi, My son fell in the zoo at the gorillas. 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."

But she swiftly descends into panic, staying on the phone while shouting to the boy: "Be calm, be calm, be calm!"

The operator attempts to reassure her that help is in hand, telling her they have already contacted the zoo's special response team.

But the mother finds it impossible to calm herself down, shouting: "He's dragging my son! I can't watch this, I cannot. I can't watch!"

Shortly after she made the call, zookeepers proceeded to shoot Harambe, the 17-year-old western lowland African gorilla, dead to save the boy - who spent around 10 minutes in the enclosure after climbing through the safety barriers and falling into the moat.

Since the shooting, there has been widespread criticism of the parents for not keeping an eye on the boy and the zoo staff for shooting the 400-pound endangered primate.

More than 470,000 people have signed a petition, "Justice for Harambe", which states: "We the undersigned believe that the child would not have been able to enter the enclosure under proper parental supervision.

"It is believed that the situation was caused by parental negligence and the zoo is not responsible for the child's injuries and possible trauma.

"We the undersigned want the parents to be held accountable for the lack of supervision and negligence that caused Harambe to lose his life."

The zoo's director, Thane Maynard, defended the zoo's barriers and actions. "The barriers are safe," he said at a press conference. "The barriers exceed any required protocols.

"The trouble is that whatever the barrier some people can get past it... No, the zoo is not negligent.

"Looking back, we would make the same decision. The gorilla was clearly agitated. The gorilla was clearly disoriented."