Abstract: Employees #1 and #2 were placing roof trusses between a brick wall and a wooden beam. They were to be placed and mounted on the beam at one end and on the brick wall at the other end, across a span of over 25 ft. A plank had been installed as a spanned beam. They had installed 30 truss members and were at the beam side of the truss installation on a 4-ft-wide walkway. The walkway was composed of 4-ft by 8-ft by 0.75-in. plywood sheeting that was approximately 32 ft long. The plywood sheeting had been installed at the top of the roof trusses and had been nailed down. The employees had not installed cross-bridging or solid blocking between the truss members to stiffen or strengthen the roof truss. Employees #1 and #2 were using an opposing pedestrian traffic pattern to lace the remaining sheets of plywood in place. They would place a sheet of plywood onto the prior sheet of plywood with a 1-ft overlap, but would not tack or nail the sheets to the trusses so as to gain the best fit before nailing. As Employee #1 picked up a sheet of plywood and walked to position it, Employee #2 passed close by going in the opposite direction to pick up the next sheet of plywood for placement. This moved the trusses and displaced them out of the hangers. Both employees fell through the roof. Employee #1 was killed. Employee #2 was hospitalized for injuries sustained in the fall.