SAN DIEGO — Most zoo visitors hope to see animals doing something other than sleeping when they visit.

But some people who visited the San Diego Zoo over the weekend saw a little more activity from one of the gorillas than anyone expected.

“Denny,” a 10-year-old lowland gorilla, broke one of the three layers of protective glass at the zoo’s Lost Forest gorilla habitat on Saturday, zoo administrators said in a statement to NBC News.

“It is common for male gorillas, especially in adolescence, to express these types of behaviors,” according to the statement. “Bursts of energy, charging, dragging items or running sideways are all natural for a young male.”

Cellphone video captured Denny running toward the tempered glass separating visitors from the gorillas and, following a “thud” and a collective gasp of “ohh” from onlookers, a large fracture in the glass was visible.

No injuries were reported. NBC San Diego reported the panel was boarded up on Monday and the exhibit was closed to the public.

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