A Utah firefighter battling the largest wildfire in California history was killed last month when thousands of gallons of flame-suppressing liquid were dropped from a Boeing 747 mistakenly flying only 100 feet (30 meters) above the treetops, according to an official report Friday. The pilot and a supervisor flying ahead in a small guide plane led the giant modified jetliner nearly into the trees on Aug. 13 because the pilots failed to recognize that there was a hill in the flight path, according to the Green Sheet report by the state's firefighting agency. Because of the near ground-level release, the retardant struck with such force it uprooted an 87-foot (27-meter) tree that fell on Matthew Burchett, a 42-year-old battalion chief from Utah helping with the Mendocino Complex Fire north of San Francisco.