Why?

This is an incident that occurred in the Ural Mountains, Russia, in 1959, where all 9 experienced hikers died. It's said they died after tearing through their tent and going outside in just their underwear, despite the temperature being -30 degrees Celsius. Furthermore, their bodies were outwardly intact but had severe fractures in their ribs and skulls, and radiation was detected. To this day, the cause of their deaths remains an unsolved mystery.