Abstract: At approximately 11:00 a.m. on September 4, 2014, an employee, a company Foreman and two coworkers were working on the roof of a 4-story apartment complex under construction. The employees were working on the building's roof installing the electrical wiring for the apartments' air conditioning units. There were several air conditioning units that needed to be connected. There were a total of five vent shaft's openings on the roof of the apartment complex, two on the north end, and three on the south end. The air conditioning units were located throughout the center portion of the roof in a rectangular pattern surrounding the vent shafts. Some of these units were placed just inches away from the roof vent shaft's openings. According to witnesses, the vent shaft's openings were all covered with OSB sheathings. Witnesses indicated the OSB sheathings were not secured and they were not marked to indicate they were being used to cover floor openings. Based on witness' statements, the employee and two coworkers were working on the north end of the roof. The employee was approximately five feet away from a vent shaft. For unknown reasons, the employee turned around and started walking towards a row of air conditioning units located on the other side of the vent shaft. The employee stepped on the OSB sheathing covering the shaft's opening. The opening was approximately 69 inches by 42 inches. The OSB sheathing gave way, falling with the employee to the ground. It was established during the investigation that OSB sheathing, 0.5 inch thick was being used to cover the opening where the employee fell. The OSB sheathing did not have any nail holes or showed any signs to indicate the sheathing had been secured to the top of the shaft's opening. The employee suffered from multiple fractures and other injuries. Emergency medical responders took the Foreman to a local hospital where he was pronounced dead at approximately 12:32 p.m.