Abstract: At 2:10 p.m. on February 22, 2019, an employee was working at a home center and retailer of building materials. The firm that employed him sold building materials. The facility had a yard and two adjacent buildings. The employee worked primarily at the warehouse/foam plastering building with one coworker. The building where the incident occurred was a one-story commercial building with a flat roof. Rainwater on the roof as leaking into the warehouse in areas. The employee climbed up a 6.1-meter (20-foot) fixed ladder attached to the building exterior to sweep the rainwater from the roof. The roof had five skylights. The skylights were not engineered to prevent falling through them. Neither fall protection nor guardrails were provided on the roof. At approximately 2:10 p.m., the employee inadvertently backed up to the base of the skylight on the northeast corner of the building. He fell through the skylight approximately 5.8 meters (19 feet) to the concrete warehouse floor below. He sustained multiple fractures. He was transported to Mission Hospital in Mission Viejo, where he was hospitalized and treated for his fractures. DOSH learned of the incident in a timely manner from the Orange County Fire Agency, which who reported the incident at 3:30 p.m. that same day. DOSH arrived at the job site and opened an investigation at 11:00 a.m. on March 1, 2019. The employee had worked for the firm for approximately nine years. The employer had three family members who shared ownership of the firm. All served as supervisors to the employee in various forms. One was the firm's general manager, and another was the firm's chief financial officer. The employee was the only person who had accessed the roof at the time of the incident. None of his coworkers were aware that he had accessed the roof until a coworker saw him on the roof from just outside a bay door. The general manager and the chief financial officer were at the other building at the time of the incident. Neither of them knew that the employee had accessed the roof. The ladder the employee used to gain access to the roof had a gate that could be locked to prevent access. The gate was not locked. A serious accident related violation was issued for failing to protect workers from falling through the skylights.