This is absolutely terrifying.

The video posted to YouTube by user Nomadic Adrenaline shows a jumper named Christopher suffering a seizure while skydiving. According to the YouTube description, the man spent 30 seconds in an unconscious free fall. Instructor Sheldon McFarlane from the WA Skydiving Academy in Australia was able to pull Christopher's parachute about 4,000 feet above ground. He regained consciousness at 3,000 feet.

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Chief instructor at WA Skydiving Academy tells ABC News that the company has safety automatic mechanisms in place to protect skydivers when they can't deploy their parachutes.