An employee was operating a forklift to lift an aluminum pallet up to a second-story mezzanine. He then got off the lift to push a button to open the mezzanine gate when the pallet slid off the base of an unassembled bin. The employee saw the moving pallet and tried to move back to dodge it. The pallet struck the employee on the shoulder, pushing him to the ground and resulting in a fractured clavicle.