An employee was preparing a Toyota trailer for transportation by placing placards on the trailer. A coworker was in the tractor cab waiting for the employee to finish preparing the trailer for transport. The parking brake on the tractor truck was not set. The tractor truck rolled back and pinned the employee between the trailer and tractor truck. The injured employee was facing away from the tractor truck at the time of the incident. The injured employee suffered crushing injuries to the midsection, ribs, and kidneys.