Abstract: At 1:20 p.m. on October 3, 2019, an employee was working as a roofer's helper for a firm that made manufactured, or mobile, homes. His employer built modular or mobile homes, some of them custom designed. The site took up 11.6 acres (4.7 hectares). The employee was working alongside two coworkers. They were all employees of this employer; that is, none was a temporary worker. The three of them were using nail or staple guns on the roof of a modular unit under construction. The staple guns shot 2-inch (51-mm) staples into wood. The employee was stapling down pieces onto the roof, when a coworker noticed that the employee had stapled through some electrical wiring. Jokingly, the employee said that he would kill himself. He lifted the staple gun and, still holding down the trigger, accidently touched the gun's muzzle up against his hat on his head. The nail gun activated. A staple went into the employee's skull, with half of the staple bent up on his hat. The employee suffered a penetrating injury to his skull. He was hospitalized and treated at a community hospital. DOSH learned about the incident by telephone at 3:40 p.m. on October 3, 2019; the employer did comply with reporting requirements. DOSH arrived at the site at 9:00 a.m. on October 14, 2019, to open its investigation. No accident-related violations were issued.