Ski Patrol Deaths May Have Been Caused by Carbon Dioxide

The ski resort's chief executive officer says the trio died after two of them fell into a volcanic fissure at the Mammoth Mountain resort... and the third tried to rescue them.
The patrol team had been on the mountain after a snowstorm, checking on a fence surrounding a natural vent that releases volcanic gas from deep within the Earth when the snow gave way causing the two to fall in.
Four other would-be rescuers were hospitalized for exposure to the poisonous gas but are doing well.