Abstract: At approximately 8:00 p.m. on April 30, 1987, Employee #1, a telescope operator, was in the console (control) room of a building housing a 4-meter optical telescope. He was preparing for the evening's observation run. He had just returned to the console room from an exterior catwalk where he had seen a cloud that had been threatening bad weather appear to be dissipating. He told the two astronomers in the console room that the weather looked good enough to start the observation run. Employee #1 opened the dome shutter and began moving the telescope to the designated position. The computer automatically energized the drive motors and began to turn the 110-foot-diameter dome clockwise. Employee #1 was crushed by the dome and killed. Employee #2 sustained an injured arm.