LONDON, Dec. 5  -- Officials at the London Zoo said the attraction's 25-year-old male silverback gorilla has died of unknown causes.

The zoo said in a statement that the gorilla, named Bongo Junior -- Bobby for short -- was found dead in his nest Friday morning, The Daily Telegraph reported.

"He was a dearly loved resident and will be sadly missed by all," a zoo spokeswoman told The Daily Mail. "Our keepers are incredibly upset, and it is asked that everyone respect the feelings of staff during this difficult time."

Ralph Armond, director-general of the Zoological Society of London, which runs the zoo, said workers and members of the public are "devastated" by the death of the "gentle giant."

"Bobby was a much-loved member of the ZSL family and leaves behind his family of keepers and three female gorillas, Mjukuu, 9, Effie, 15, and Zaire, 34," Armond said. (UPI)