Visitors at the Henry Doorly Zoo and Aquarium captured the encounter on video Thursday. The gorilla charged the glass shortly after video showed a young girl pounding her chest.
The zoo said Kijito, a 24-year-old, 375-pound western lowland gorilla, cracked the first of three panes of glass.
"The glass on the exhibit is engineered to account for the size, strength and speed of a large male gorilla," zoo officials said in a statement. "While one layer of glass on the exhibit did crack, leaving two layers untouched, the public was never in danger and the exhibit remains open."
Zoo officials said the gorilla's actions may have had nothing to do with the girl seen pounding her chest, a behavior exhibited by gorillas to intimidate others.
“Although the gorilla may have been engaging with the public to receive a reaction, the gorilla was most likely exhibiting typical gorilla behavior and likely posturing toward another male gorilla," Dan Cassidy, the zoo's general curator, said in a statement. "It is common for male gorillas to display to each other and occasionally they use the glass because of the noise it makes on their side.”