MOSCOW — It was supposed to be a thrilling ride down a ski slope inside a giant inflatable ball; it ended in tragedy for the two Russian men inside.

The transparent plastic ball — known as a zorb — veered off course and sailed over a rock ledge in the rugged Caucasus Mountains of southern Russia. The ball picked up speed as it flew down the steep slope, rolling and bouncing. One man was killed and the other badly injured.

The man who died, 27-year-old Denis Burakov, was with friends at the Dombai ski resort, where they frequently went snowboarding, on Jan. 3 when he decided to take a ride in a zorb being operated next to a beginners' slope. His friend Vladimir Shcherbakov joined him.

An eight-minute video taken on Burakov's phone by one of his friends shows the two men being fitted into harnesses inside the zorb, which consists of two polyurethane balls with a layer of air between them. The zorb is then released to roll down the hill, the two men spinning inside.

But the zorb bounces off of the intended path, and a man waiting for it at the bottom of the hill tries in vain to catch the ball before it pops over a rocky ledge and disappears down a gorge.

Both men were ejected from the zorb as it tumbled and they landed on the snow about 30 feet apart after having rolled about a mile.