A video taken at a zoo in China on Monday that has gone viral shows a live donkey being fed to tigers in front of the public, an incident that has fueled concerns about the welfare of the animals at the facility and at Chinese zoos in general.

In the video, reportedly shot by a visitor at the Yancheng Safari Park, just outside Shanghai, a group of men in raincoats push a donkey down a wooden ramp into a moat where two tigers pounce on it. At one point the donkey thrashes around underwater.

The footage shows only the beginning of the ordeal, but the South China Morning Post reports that it took a half hour for the donkey to die.

Disgruntled shareholders were behind the incident, according to a statement (in Chinese) issued by the zoo. Angered by a lack of financial returns from the zoo, the shareholders arranged for the group of men to capture some of the animals, including the donkey, and sell them to people outside the facility. After being stopped by security, the men decided instead to push the donkey into the tiger enclosure to at least “save on animal feed,” one shareholder told The Guardian.

“It’s a terribly sad video because everything in it is suffering, whether it’s the donkey, whether it’s the tigers, whether it’s the public watching them,” says Doug Cress, chief executive officer at the World Association of Zoos and Aquariums, a body that accredits zoos but has no affiliation with Yancheng Safari Park.

Cress says the incident should never have happened. “If the zoo had the proper barriers between humans and the enclosures, first you couldn’t have gotten the animals out of the enclosure, and second, you couldn’t have tossed them into the tiger enclosure. Clearly the barrier and safeguards aren’t effective at that zoo.”

At press time, the zoo had not yet responded to National Geographic's request for comment.

This incident is the latest in a string of disturbing events involving Chinese zoos, which have earned a reputation as lacking in animal welfare standards. According to Cress, new wealth in China has led to a boom in zoo and aquarium businesses during the past 20 years, but a respect for animals and an understanding of best welfare principles has lagged behind.

Zoo visitors in China have been known to throw rocks and garbage at animals. And sometimes animals are forced to perform for the public, an activity that respected accrediting agencies criticize on grounds of animal mistreatment.

Dave Neale, animal welfare director with the Hong Kong-based nonprofit Animals Asia, says he’s horrified about what happened at Yancheng Safari Park—but not surprised. When he’s visited the zoo in the past, visitors have been allowed to pay for live ducks and chickens to throw in lion and tiger enclosures for entertainment.

In rare instances he’s seen other facilities offer live sheep, goats, pigs, and cows for predators to feast on. “If someone pays enough money, some parks are willing to do anything,” he says. “It undermines the educational value of a zoo—I don’t see the educational value to something like that.”

Neale says this kind of cruelty is found most often in non-urban safari parks, which are overseen by China’s State Forestry Administration, rather than facilities such as Beijing Zoo and Shanghai Zoo, which are run by city departments and focus more on conservation than entertainment.

Yangcheng Safari Park is accredited by the Chinese Association of Zoological Gardens, according to Neale, an organization that he says has good intentions but lacks the resources to enforce strict animal welfare standards for its members. The association has not yet responded to National Geographic’s request for comment about whether it plans to take action in response to Monday’s incident.

Aside from the zoo’s inadequate barriers, Cress says, this incident reveals another problem: Zoo tigers simply aren’t meant to eat live animals. While tigers in the wild kill a diverse array of animals for food—from deer and water buffalo to, occasionally, domestic livestock—upstanding zoos feed their tigers beef and horse meat, not living, breathing animals.

“It wasn’t hunger that drove those two tigers; it was curiosity,” Cress says. “They don’t seem to have the understanding of how to bring down an animal like this and what to do about it, really.”

Indeed, while the tigers in the video do attack the donkey, it’s hardly the sort of clinically efficient predator killing you see in nature documentaries. In the wild, a tiger stalks its prey and can kill it within minutes by clamping on its neck.

And, Cress notes, a lack of predator instinct in captive tigers could actually cause them harm if a horned animal, for example, was thrown into their enclosure.

“The safety of the animals and people should be the number one priority,” Neale says, “so the zoo is very much at fault, even though hopefully it’s a one-off incident.”