An employee stepped up on the back of the work vehicle which was parked at a customer parking lot and began manually unloading a 4 galvanized pipe from the ladder rack on top of the vehicle. While removing the pipe, the employee lost his balance and fell backward off the back of the vehicle. The pipe that the employee was unloading was pulled down as he fell. Upon landing on the concrete parking lot, the pipe pinned the employee s right hand against the concrete. The employee sustained a fracture and laceration to their middle finger that resulted in medical amputation of the finger.