An employee was emptying a self-tipping dumpster that was attached to the forks of a forklift. He tilted the forks forward to help facilitate the dumping of the dumpster. He then got out of the cab of the forklift, walked to the side of the forklift mast, and placed his left hand on the lower portion of the mast. He reached up with his right hand and disengaged the release lever on the back of the self-tipping dumpster, causing the dumpster to quickly shift forward. The resulting shift in weight of the dumpster caused the forklift forks to swing back into the mast, pinching the employee's ring finger between the forks and mast. The tip of his ring finger digit was amputated.