On June 15, 2003, a 39-year-old male career Lieutenant (Victim #1) and a 39-year-old male career fire fighter (Victim #2) died while trying to exit a commercial structure following a partial collapse of the roof which was supported by lightweight metal trusses (bar joists). The victims were part of the initial entry crew searching for the fire and possible entrapment of the store manager. Both victims were in the back of the store operating a handline on the fire that was rolling overhead above a suspended ceiling. A truck company was pulling ceiling tiles searching for fire extension when a possible backdraft explosion occurred in the void space above the ceiling tiles. Victim #1 called for everyone to back out due to the intense heat. At this point, the roof system at the rear of the structure began to fail, sending debris down on top of the fire fighters. Victim #1 and Victim #2 became separated from the other fire fighters and were unable to escape. Crews were able to remove Victim #2 within minutes and transported him to a local hospital where he succumbed to his injuries the following day. Soon after Victim #2 was removed, the rear of the building collapsed preventing further rescue efforts until the fire was brought under control. Victim #1 was recovered approximately 1 1/2 hours later. NIOSH investigators concluded that, to minimize the risk of similar occurrences, fire departments should: 1. ensure that the first arriving company officer does not become involved in fire fighting efforts when assuming the role of Incident Command; 2. ensure that the Incident Commander (IC) conducts an initial size-up and risk assessment of the incident scene before beginning interior fire fighting operations; 3. conduct pre-incident planning and inspections for mercantile and business occupancies; 4. ensure that ventilation is closely coordinated with the fire attack; 5. ensure that fire fighters immediately open ceilings and other concealed spaces whenever a fire is suspected of being in a truss system; 6. ensure that fire fighters performing fire fighting operations under or above trusses are evacuated as soon as it is determined that the trusses are exposed to fire; and, 7. consider using a thermal imaging camera as a part of the size-up operation to aid in locating fires in concealed areas. Additionally, municipalities should consider requiring specific building construction information on an exterior placard.