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The silverback gorilla seems to come from nowhere as he launches himself at the reinforced glass wall of his enclosure - in an attempt to attack the startled family watching on the other side.

Their hearts must have been racing as the glass cracked with the force of his impact. Luckily, it was strong enough to hold firm and the animal was not able to break through and attack.

Still, we bet they will be having flashbacks to that moment for a while.