Abstract: At 2:30 a.m. on July 30, 2019, four employees were working as carpenters for a framing contractor. They were performing exterior carpentry in a project of new work on or an addition to a single-family or duplex dwelling. The building was 45 feet wide by 60 feet long, with 12 foot 6 inch-high wood walls. It was set on a 5-foot poured concrete wall. In metric dimensions, it was 13.7 meters wide by 18.3 meters long, with 3.8-meter-high wood walls. It was set on a 1.5-meter poured concrete wall. The workers were setting flat roof trusses on a pool elevation wall system. The trusses were long. They were 47 in. high (1.19 meters high) and 47 feet long (14.3 meters long) including the tails. The employees were working one story up. The trusses collapsed, falling over in domino fashion. The employees fell one story to the concrete below. All four employees were injured. Two of the employees were hospitalized, and two of the employees were treated without hospitalization. One employee was hospitalized with a pelvic contusion and a bilateral hip sprain. The employees had improperly braced the trusses with truss lock spreaders and toe nailing into the top wall plate. The Building Component Safety Information (BCSI) B2 summary sheet stated that temporary installation restraints or bracing must be applied to all planes of the trusses to ensure stability. Here, the east end wall bracing was not 8 feet (2.4 meters) on center, and the ground bracing was not in line with the wall bracing. There was not any top or bottom chord bracing in place.