At ~ 2:43 PM, Westmoreland 911 dispatched Station 20 (Murrysville VFC) for an Automatic Fire Alarm (AFA) at the Blue Spruce Shopping Plaza. Station 20 responded with Engine 20 (4 firefighters including Assistant Chief 20), with 1 firefighter going directly to the scene, and 2 firefighters on standby at the station prepared to deploy Truck 20. Westmoreland 911 also dispatched the following stations to support Station 20: Station 64 (White Valley VFC), Station 22 (Export VFC), Station 78 (Sardis VFC), and Station 236 (Holiday Park VFC). Captain and Sergeant 64 were first on scene, and observed no fire or smoke coming from the structure. Engine 20 arrived with Assistant Chief 20 establishing the command, and upon investigation found that the accidental pulling of a fire alarm pull box had activated the Complex AFA System. Command 20 returned all responding units except for Engine 20. The pull box was reset, however the firefighters found that there was a fault in the Shopping Plaza's AFA System Control Panel, so the system could not be reset. The Shopping Plaza's Management Company and Fire Alarm Company had been notified, and representatives were enroute to correct the fault. All businesses were notified of the fault in the Plaza's AFA System. Command 20 returned Engine 20 to service and station.