Updated

A viral video that appears to show a visitor at the Los Angeles Zoo hop a fence, sneak up from behind and spank a hippopotamus has prompted a police investigation, The Los Angeles Times reported.

The bizarre video was posted last week and showed the unidentified man approach the two hippos, named Rosie and Mara. Rosie, 4, was the one who was spanked. The report said the hippo did not have any visible injuries, but an encounter like that could be stressful.

“We seriously feel this was an isolated incident,” April Spurlock, a zoo spokeswoman, told the paper. “Most people know not to go in with the animals. It’s common sense.”

Hippos are dangerous animals. Last weekend, a tourist from Taiwan was killed in Kenya during an attack and, in another incident, a local fisherman was mauled to death.

Hippos are the world’s deadliest large land animal due to their aggressive nature and sharp teeth. The animals can weigh up to three tons and kill about 500 people in Africa every year, the BBC reported.

Fox News' Katherine Lam contributed to this report