A 10-year-old western lowland gorilla shattered part of the protective glass in its habitat at the San Diego Zoo on Saturday, zoo officials confirmed.

According to a statement from the zoo, the incident took place on October 11, when the gorilla — named Denny — broke through one of three layers of tempered glass that separate the animals from visitors in the Gorilla Forest habitat. Another gorilla was also in the area at the time.

“Denny was not injured,” the zoo said in a statement. “Both gorillas will be cared for behind the scenes until the panel is replaced.”

Officials emphasized that the glass barrier consists of three protective layers and that only one was damaged. No visitors or staff were harmed during the incident. The impact startled onlookers who witnessed the moment.

“We were looking down at our phones and didn’t notice that the gorilla had taken a running start and jumped into the glass. He hit it with his elbow, right in front of my face,” said Katya Sutil, who was celebrating her birthday at the zoo with her sister. “When it hit, I was so shocked I stumbled back a few feet. When I looked up, the gorilla was staring directly at me, and then I saw a giant crack — about six feet long. It was pretty big.”

So far, the zoo has not announced when the gorilla habitat will reopen to the public.

“For the 20 minutes we were there, the gorillas kept running back and forth, kind of provoking each other. One would charge at the other and then disappear, and then it would happen again,” Sutil added. “Maybe there was some tension between them.”

Western lowland gorillas, like Denny, are critically endangered species native to the forests of Central Africa. The San Diego Zoo is involved in conservation programs to help protect these primates and their natural habitat.

Information from Fox5SanDiego