Most of the people who died in the Mt St Helens explosive eruption of 1980 died from what volcanic emission?

The eruption blasted ash and gases into the atmosphere. Winds carried ash great distances. The ash-covered truck shown here was parked 19 kilometers (12 miles) from Mount St. Helens. Two men who were camped nearby died, suffocating from hot volcanic ash. They were two of 57 known fatalities.