Abstract: Employee #1 was operating a Hi-Ranger bucket truck that was positioned behind a Manitowoc boom truck being operated by a coworker as they installed insulators on a cement pole. Employee #1 was just starting to lower the lower boom of the Hi-Ranger when the boom of the Manitowoc began to swing at a high speed to the right. The coworker grabbed the controller but it would not stop. The Manitowoc boom swung so fast that it put enough tension on the bucket truck boom to break the hold-back cable and continued to push the upper boom over. This released the leveling cables on the Hi-Ranger bucket truck and caused it to flip over, throwing Employee #1 out of the cab. He fell to the ground and sustained fatal head injuries. When the remote controls were later tested, the remote START button was hit and the swing controller actuator pulled the swing lever full right. When the emergency STOP button was hit, it would kick out of neutral, but when it was pulled on again the swing lever went to full swing right. There was apparently a malfunction with the controller. Further evaluation showed that the servo-actuator had also malfunctioned.