Abstract: At 10:30 a.m. on February 18, 2017, three employees were assisting in the restoration of a movie theater. The employees were working to install three speakers, weighing approximately 150.5 pounds, on a newly constructed lower level ceiling platform of the theater. The upper level ceiling platform was adjacent to a stairwell with concrete floor beneath. The distance measured from the upper ceiling platform to the concrete floor was approximately 18 feet and approximately 13 feet from the ceilings lower platform. The ceiling was held in place by 9 studs made of 25-gauge metal that were spaced 2 feet apart on center. The employees were instructed to transport the three speakers form the upper ceiling platform to the lower platform for installation. As Employee #2 worked from the upper level platform, handing the speakers to Employee #1, who was standing on a ladder that was resting on the lower level ceiling platform, one of the speakers crashed through the ceiling. Employee #2 fell through the ceiling platform and struck the concrete floor at the bottom of the stairwell with one of the speakers landing on him. Employee #3, who was standing beneath the lower platform holding Employee #1's extension ladder, was struck by the ceiling. Both Employees #2 and #3 were hospitalized and treated for their injuries that included a torn ligament on one of Employee #3's feet. Employee #2 was not injured. The incident investigation revealed that tap gun screws that were intended to be installed to further secure the ceiling to the building's masonry block wall were not installed prior to the speaker installation. This led to an unstable work surface and collapse of the lower ceiling platform.