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. Playful: The little girl can be seen in the window beating her chest at one of the gorillas . Cross: But the gorilla's friend in the background isn't quiet as keen on the game . Sprint: And he decided the time had come to do something about it - so started running towards the glass . Heavy: The gorilla throws his entire weight at the pane of glass at Omaha's Henry Doorley Zoo . 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.' Horror: The family's terrified reactions were captured in the glass the moment they gorilla hit . Impact: The force is so much the glass cracks on impact - sending the family fleeing . Huge: Mountain gorillas like this one can weigh as muhc as 485lb, or 220kg . 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.
Toddler filmed beating her chest at the Silverback at a Nebraska zoo.
Gorilla then takes a run at the glass - and hits it with such force it cracks.
The footage captures the terrified family running for their lives.
Video of Thursday's incident has got  126,000 views since it was uploaded.