A gorilla that the Philadelphia Zoo was trying to mate with a newly arrived female died suddenly Friday, zoo officials said.

Jabari, a 28-year-old western lowland gorilla, had shown signs of mouth or throat discomfort and apparently lost his appetite Thursday. That led to a full examination under anesthesia Friday, officials said.

While anesthetized, Jabari stopped breathing and could not be resuscitated, officials said.

"As soon as he fell asleep, we knew there was something dramatically wrong," said Keith Hinshaw, the zoo's senior veterinarian.

Preliminary findings from a necropsy showed that Jabari had suffered severe inflammation under the base of his tongue, which led to swelling in the back of his throat, Hinshaw said.

The cause of death will be determined after further analysis, which could take weeks.

"We are shocked and deeply saddened by this tremendous loss," said Andy Baker, the zoo's chief operating officer.

"Jabari was an iconic favorite with our staff and visitors, and we expected him to be with us for many years," Baker said.

The typical life span of a gorilla is 30 to 50 years. The oldest gorilla in the zoo's history was Massa, who was born in the wild and lived to be 54. He died in 1984.

Jabari was born in 1985 at the Brookfield Zoo in Chicago. He arrived in Philadelphia from the St. Louis Zoo in 2004.

In June, 14-year-old Kira arrived in Philadelphia from the Franklin Park Zoo in Boston.

Philadelphia Zoo officials had hoped the pairing of Jabari and Kira would lead to the first baby gorilla born at the zoo in decades.

The zoo has four other western lowland gorillas. The species is listed as critically endangered.