Kimberley Ann Perkins O'Connor told CNN that she was trying to take a picture of a 17-year-old male gorilla named Harambe, who was peeking out of his cave, when she heard a splash and then a man screaming. A child had fallen into the gorilla's enclosure.
The sound attracted Harambe, who barreled over to the moat, saw the child and then knocked the boy against a wall, O'Connor said.
O'Connor, who recorded much of the scene
on her phone, said the gorilla didn't seem intent on harming the boy at first.
"He dragged the child a little further down into the moat and he ... almost looked like he was helping him, pulled his pants up, stood him up, and then all of the sudden everybody started screaming again, and he pulled him completely out," she said.
Another witness, Tangie Hollifield, told CNN affiliate WCPO
that she hugged a member of the child's family and assured him the boy would be saved.
"He was just flipping out -- just scared," she said. "The scream from that gorilla, that I have never heard. I don't think that he was hurting him. He was just protecting him."
'It was a mess'
The screaming seemed to agitate the 450-pound primate, witnesses said, and the scene quickly deteriorated
. The gorilla became more aggressive and was seemingly determined not to free the child, witnesses said.
"From what we saw [the child] could have been killed at any second," Bruce Davis, who was with Hollifield, told WCPO. "He threw him 10 feet in the air, and I saw him land on his back. It was a mess."
O'Connor said the boy tried to free himself on at least one occasion. "[Harambe] pulled the boy back in, tucked him underneath and really wasn't going to let him get away," she said.
Harambe had the boy between his legs and was hovering over him, she said.
"I saw him when he was on top of the habitat, dragging the boy, pulling him underneath him. It was not a good scene," O'Connor said. "He literally picked the boy up by his calf and dragged him toward another cave to basically get him out of the view of this crowd that hadn't yet dispersed."
The boy had gotten into the enclosure by going under a rail, through wires and over a moat wall, according to the zoo.
O'Connor said she heard the boy joke with his mother about going into the moat. The mother was then briefly distracted by other children with her, and suddenly the boy was in the water, O'Connor said.
O'Connor said a special team tasked with dealing with dangerous animals responded quickly and ushered the crowd away from the scene. That spared onlookers from seeing officials use a rifle to take down Harambe.
"My niece and I were the last ones exiting, and as soon as we heard the shot, we knew what had happened," O'Connor said.
The boy was treated at a local hospital and released on Saturday evening, according to officials.
The debate around Harambe's death
Officials made the decision to shoot Harambe because the boy was in "imminent danger." They feared a tranquilizer would take too long to kick in, and the dart may have agitated the gorilla.
"There was nobody getting that baby back from that gorilla -- no one was taking him," Hollifield said.
The killing has prompted a debate
on whether keepers had to kill Harambe. Some point to past cases at zoos where officials had managed to retrieve people from gorillas without harming the primates.
An online petition seeking "justice for Harambe" through criminal charges has earned more than 162,000 signatures.
Western lowland gorillas are critically endangered in the wild, numbering fewer than 175,000, according to the zoo. An additional 765 gorillas dwell in zoos worldwide. The zoo had hoped Harambe would father more gorillas.
Davis said critics of the killing didn't have enough information to properly judge the zoo's decision.
"You could look in their eyes and tell they had a tough decisions to make," he said. "It was basically the child or the gorilla, and they chose ... a lot of people say poorly ... but they didn't see. I saw it."