Document everything that is happening. Try and have a one on one sit-down with this person. If he refuses, then try and get a sit-down with the both of you and the boss. The place I work at now, we had a pilot who was unsafe, broke the rules, etc. Everyone knew this. But anytime he was going somewhere, and he had room, he would take that person if they asked. He went on a flight one night, carrying this ride-along up front (C-421) and he had 4 passengers in the back. A mother and her 3 kids. The weather into the airport was not so good. He was so concerned trying to get his clearance in the air to leave this airport after he let off his passengers while shooting a GPS approach, he did not pay enough attention, busted minimums, flew through trees, and crashed. He and the ride along, and one of the kids in the back (8 years old) were killed. Try and explain that to the surviving mother and the other two kids, and her husband.