Abstract: At 5:15 a.m. on May 17, 2019, a coworker, a Lead Technician and Employee #1, a Mechanical Technician, were performing maintenance on an amusement park ride. The 12,500 pound vehicle consists of the chassis assembly, which rides on a track, and a twelve passenger cabin assembly, which weighs 4,500 pounds. These two components are connected by a motion system assembly that is comprised of various mechanisms including, six electro-mechanical DOF actuators, and a yaw ring. The yaw ring provides rotation to the cabin and the DOF actuators control the vertical height of the cabin as well as other motions such as tilting and rolling. Under normal operation, the vehicle is controlled by a computer system and is programmed to complete a cycle of specific motions. While maintenance is being performed, the main power provided by the track is locked out and tagged out of service at the 240-volt panel and only certain functions are still accessible, and controlled only by a 24-volt battery backup. The coworker locked out and tagged out the electrical panel. Employee #1 climbed under the raised cabin assembly to access the grease fitting and connect the grease gun on the underside of the yaw ring. The coworker was adjacent to the vehicle while operating the controls via battery backup. He engaged two switches required to release the yaw brake, including a motion system override switch and a yaw brake release switch, allowing the cabin assembly to rotate freely to grease the yaw ring. When the coworker disengaged the brakes for the yaw, the brakes for the DOF actuators also unexpectedly released. The 4,500 pounds cabin assembly immediately lowered onto Employee #1, while he was laying on his side. Employee #1 was caught between the cabin assembly and the chassis assembly and was unresponsive. The coworker was limited on how quickly he could attempt to raise the cabin assembly off of Employee #1 because he had to unlock the track power at the electrical panel and boot up the computer system that fully controls the vehicle. While waiting for the computer to boot for several minutes, the coworker attempted to use a floor jack to lift the cabin assembly off of Employee #1, but to no avail. The computer system indicated a fault so Employee #1 had to control and raise each DOF actuator individually until there was enough space to release Employee #1, but he was still unresponsive. Employee #1 was killed from compressional asphyxia and chest injuries.