It started out as a sweet family moment on a day trip to the zoo: a little girl beating her chest at a gorilla, safely separated by a pane of glass.
But it seems the Silverback at the Nebraska zoo was less amused.
The massive animal – who had been standing at the back of the enclosure – clearly decides enough is enough, and runs at the onlookers.
The gorilla then launches himself, and his hundreds of pounds, at the little girl, hitting the glass with such force it cracks.
The terrified family have fled to safety in the meantime.
The incident took place at Omaha’s Henry Doorley Zoo yesterday, and since it was uploaded to YouTube it has had more than 126,000 views.
Writing on Reddit, the person who uploaded the video revealed: ‘The person added: ‘Shortly before this we were telling the kids they could not break it. They will never believe us again.
‘Sadly the one beating her chest really started crying.’
They added: ‘I came back a couple of minutes later, and the zoo keepers were telling people to stay away.’
Male mountain gorillas, which can reach the age of 40, weigh between 300 and 485lb (220kg).
They are classified as an endangered species, and Henry Doorley Zoo is famous for its gorilla breeding programme.
The zoo was responsible for the first gorilla test tube baby in 1995, and now boasts the largest gorilla sperm bank in the world.