how did he die?
He was killed by the 1980 eruption of Mount St. Helens
David A. Johnston
David Alexander Johnston (December 18, 1949 – May 18, 1980) was an American United States Geological Survey (USGS) volcanologist who was killed by the 1980 eruption of Mount St. Helens in the U.S. state of Washington. 
mount st helens is on what type of plate boundary Cascade Volcanic Arc where is it located? Skamania County, Washington, in the Pacific Northwest region of the United States. describe the geographical aspect of the former county? Its total area; (1.7%) is water. 90% of Skamania is forested and 80% is a part of Gifford Pinchot National Forest. in which state is the county? Washington how did the human get affected by the 1980 eruption? Fifty-seven people were killed; Harry R. Truman and David A. Johnston is the mount important to any tribe? Native American lore contains numerous stories to explain the eruptions of Mount St. Helens and other Cascade volcanoes. what is scientific about the aforementioned latter person? He was an American United States Geological Survey (USGS) volcanologist which rescue effort was he a part of? USGS team rescue efforts is he alive? No
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David A. Johnston [SEP] Introduction
David Alexander Johnston (December 18, 1949 – May 18, 1980) was an American United States Geological Survey (USGS) volcanologist who was killed by the 1980 eruption of Mount St. Helens in the U.S. state of Washington. A principal scientist on the USGS monitoring team, Johnston was killed in the eruption while manning an observation post away on the morning of May 18, 1980. He was the first to report the eruption, transmitting "Vancouver! Vancouver! This is it!" before he was swept away by a lateral blast. Despite a thorough search, Johnston's body was never found, but state highway workers discovered remnants of his USGS trailer in 1993.