Story of the 'Valley of the Headless Men'

The Northwestern Territories of Canada are truly one of Earth’s last true wild places. One of its special National Park Reserves, called the Nahanni Valley, is however a little bit wilder than most. It is home to some strange myths and mysteries and boasts a fearsome reputation for being a haunted and deadly place. This remote wild valley is not just inhospitable due to its rugged terrain, extreme weather, and predators, but is also deadly due to some unexplained circumstances. Over the decades, many unfortunate travelers and explorers have gone missing, or they turned up dead and beheaded. The number of decapitated bodies found within Nahanni Valley have earned it the nickname “Valley of Headless Men”. What is the explanation to this mystery?