In 1924,hundreds of thousand-year-old skeletons were found under the ice of Lake Roopkund in the Himalayas. Many had holes in their skulls. But they weren't hurt in any other way. Scientists thought the people must have been hit from above. But for years, the cause of their death was a mystery. Today,scientists think these people were killed by giant hailstones-balls ofice . Hailstones form when raindrops high inthe sky cannot hold them at speeds of over 160 kilometers an hour. For the unlucky people at Lake Roopkund, there was now here to run. They were all killed by the hailstones.