Abstract: At 3:45 p.m. on January 20, 2020, an employee (Mechanic) was assigned to work on a loose chassis and side fairings on a Volvo model 660 semi-truck and secure any loose components by bolting them with a wrench. The employee was also told to remove the driver side front axle wheel for brake inspection. The employee placed a Craftsman 20-ton hydraulic bottle hand jack under the truck's driver side jacking point and raised it a few inches. The employee removed the front axle wheel and drum brake and slid under the vehicle on a roller creeper. The employee was under the area behind the driver door on his back looking up at the underbody. The parking brake had been set but the air bags were not deflated prior to starting work and no additional lifts, jack stands, wheel chocks or other restraining means were used. Multiple jack stands and wheel chocks were immediately available. While the employee visually inspected the underbody without using any hand tools, the truck unexpectedly shifted forward and fell off the jack. The shift was likely caused by an ongoing pressure drop in the suspension air system due to naturally occurring leaks imposed by forces on the vehicle. The employee was working alone and there were no direct eyewitnesses and no surveillance footage. Coworker #1 (Owner) and Coworker #2 (Truck Owner) responded to the scene and quickly initiated extraction efforts by driving a shop forklift around the building to lift the truck's front to remove the employee. Coworker #1 also called first responders to the scene by calling 911. Coworker #3 assisted directing Coworker #2 inserting forks and maintaining the lift while he pulled the roller creeper with the unconscious employee out. The employee's upper body was crushed and his jaw broken, requiring hospitalization. The employee subsequently incurred cardiovascular damage, brain damage from two strokes after losing his pulse for approximately 45 minutes and other serious health complications due to the accident.