There'* a longer version of that video with about 20 guys doing the exact same thing. There is only one guy in the whole video who actually manages to fire the rifle without losing it, and oddly enough, he'* a little guy too. Proper technique goes a long way.
The rifle itself is a Rogue River chambered in .577 T-Rex. It'* a HUGE cartridge, designed for hunting large African game. Single shot Elephant killer in other words. About 12,000 ft. lbs of energy at the muzzle. For comparison, a .50BMG delivers about 9,000 ft.lbs, and a typical Remington 700 in .375 H&H delivers around 5k.