In this video doing the rounds today, a family learn a valuable lesson while watching Silverback gorillas at the zoo when the alpha male puts on a terrifying display of dominance - resulting in a cracked window and our hearts jumping into our mouths.
The speed at which he moves is unbelievable. Commenters online have been speculating if the little girl beating her chest at the beginning of the video triggered the display.
The incident is believed to have taken place at the Omaha Zoo in Nebraska.
Some also pointed out that if you pause the video at 0.09 seconds, the family's reaction is brilliantly framed in the window.