‘Leo,’ a red panda at Brookfield Zoo, died unexpectedly.

The loss of the red panda Leo has left the Brookfield Zoo in a state of mourning.

The zoo made the sad announcement on Wednesday morning that Leo, age 5, had unexpectedly passed away. There was no indication of what caused the death.

In 2018, he moved to the Hamill Family Wild Encounters habitat at the Brookfield Zoo, where, according to the zoo’s staff and visitors, “he quickly won over the hearts of his caretakers and zoo patrons while he spent time in his habitat.”

Cranberries that had been dried out were his favorite snack, and he was always ripping up paper boxes.

The World Wildlife Fund estimates that there are fewer than 10,000 red pandas in existence across the globe.