In the night of what is believed to be February 2, 1959, 9 Russian university students hiking and skiing in the wilderness of the Ural mountains died mysteriously. Theories for their demise range from natural disasters to a government or military cover up and even to an encounter with aliens or the Russian bigfoot known as Yeti. Known as the Dyatlov Pass Incident and still famous today.
http://www.historyandheadlines.com/russian-bigfoot-kills-9-students-dyatlov-pass-incident/
I am fascinated by that historical event.
Acute radiation poisoning? That’s the theory I find most plausible, if there even IS a theory that’s plausible.