Otto the river otter, a resident of the Bays Mountain Park and Planetarium in Tennessee. died this month after a sudden illness.

The week before his death, a zoo visitor had reportedly tossed some food into his enclosure – soon after which he fell ill. While it is not known exactly what the visitor gave him, a zoo worker found the remnants of grapes in the two-year-old’s habitat.

“Human food is often intolerable and, in this case, even harmful to our animals,” the park wrote in a Facebook post, adding that they would be performing a necropsy to ascertain the reason of death.

Hundreds of people shared photos and videos of Otto on Facebook following his death.

Otto was nine months old when he came to the park in October 2017 from a rehabilitation facility in North Carolina where he and his siblings had been recouping after they lost their parents in a flood. “The hope was to release them back into the wild, but the pups had lost their fear of humans, so Otto found a new home with us at Bays Mountain Park,” a Facebook post said.

The zoo is now looking to find a new otter to replace Otto.