The San Francisco Zoo lost one of its brightest lights when its youngest gorilla was killed by a closing hydraulic door.

Kabibe, a lowland gorilla who was almost 16 months old, captured the hearts of San Franciscans as an underdog who triumphed over life’s challenges. She was one of the nation’s few gorillas born in captivity each year and prevailed despite long odds. As a baby, she was underweight and even her own mother rejected her. But she found a way to survive and thrive.

“Some animal deaths are more difficult to process than others, and this tragedy has struck us all in the deepest way imaginable,” Tanya Peterson, the zoo’s executive director, said Saturday in a statement announcing the young gorilla’s death.

The accident took place Friday night as the animal keepers moved the gorillas to their night quarters after the zoo closed. According to officials, Kabibe unexpectedly darted under the hydraulic door as it was closing.

Zoo officials called this type of accident “extremely rare” and are looking into how and why it happened. They promised to review policies, procedures and training to see if any changes are needed.

Activists disturbed

Kabibe’s death disturbed some animal activists, who say better safety measures could have prevented such an accident. There have been at least two other fatal incidents involving animals and hydraulic doors at zoos in Washington, D.C., and in Canada.

One solution could be a mechanism installed in those hydraulic doors so zoo staff could push a button that would stop the door from closing or reverse the motion, said Elliot Katz, a veterinarian and founder of In Defense of Animals.

That would “stop the movement of the gate, so the animal isn’t crushed or killed,” he said.

It’s unclear whether the San Francisco Zoo’s door had that mechanism. A zoo spokeswoman didn’t immediately respond to The Chronicle’s inquiry.

Fans devastated

Kabibe’s fans were saddened to hear of her tragic death. There were no signs near her enclosure that noted her passing, zoo visitors told The Chronicle. That was far from the pomp and celebration when Kabibe first arrived on the scene.

Denise and Michael Henley made the trek from Vallejo to the San Francisco Zoo on Saturday, bringing their two young grandchildren with them. The Henleys hoped to say hello to Kabibe at the gorilla preserve but instead saw gorillas in mourning.

One of the females carried a tree branch on her back, said Michael Henley, who has visited the zoo over the past eight years. He thought it was odd when Kabibe didn’t show after they waited for 10 minutes.

“To have a door slam on her is devastating,” Henley said. “You want to see them get bigger and bigger and grow up.”

This isn’t the first time the San Francisco Zoo has run into problems with its animal care.

On Christmas Day 2007, a female Siberian Tiger named Tatiana escaped from her grotto and killed a teenage boy and injured two others before she could be shot to death by police. In the past decade, the zoo also received criticism for its treatment of elephants.

Other zoos’ problems

The two previous incidents at other zoos involving animals killed by hydraulic doors prompted action. The National Zoo in Washington, D.C., changed the wording of its safety guidelines and made repairs to the door after a monkey was killed in 2005, according to the Washington Post. A fatal 2009 accident involving a capybara and a hydraulic door pushed the Calgary Zoo in Canada to suspend one of its employees, CTV News said.

Kabibe, whose name means “little lady” in Swahili, was born July 17, 2013, to parents Nneka and Oscar Jonesy. But her name was chosen by her fans, who paid $1 to vote for what the young gorilla would be called. Kabibe beat Kenura, which means “joy” in the Kikuyu language, and Malaika, which in Swahili means “heavenly messenger.”

Kabibe faced challenges early on. As a baby, she weighed roughly 8 pounds — too little for a baby gorilla — and her birth mother ignored her. So the zoo staff raised Kabibe until she was 6 months old.

Endangered species

Kabibe was gradually introduced to the rest of the gorilla family, first with the family matriarch, Kabibe’s grandmother Bawang, who had also raised Kabibe’s brother, Hasani. Bawang and Kabibe immediately bonded and became inseparable, the zoo said.

Kabibe’s home at the zoo — the Jones Family Gorilla Preserve — will remain open after the accident.

Kabibe’s species, the Western lowland gorillas, is endangered, with 750 living in captivity and roughly 100,000 living in the wild in Central Africa. The population has plummeted more than 60 percent in the past 20 to 25 years because of disease and poaching, according to the World Wildlife Fund.

Meanwhile, zoo staff members are grieving. Bob Cooney, the zoo’s vice president of guest experiences, said Kabibe had her own fan club.

“All of us here are just heartbroken,” Cooney said. “It’s heartbreaking, just heartbreaking.”

Jaxon Van Derbeken and Wendy Lee are San Francisco Chronicle staff writers. E-mail: jvanderbeken@sfchronicle.com, wlee@sfchronicle.com