During an emergency, determining accurate location of victims is crucial for expediting rescue efforts. In this paper, we present a mass-deployable active RFID RSSI-based real time locating system to localize victims at an emergency site. The system architecture, localization algorithms and experimental results are discussed in the paper. The system includes commercial off-the-shelf active RFID readers which are rapidly deployed at known points at the emergency site. A paramedic carrying around a bag of Active RFID tags attaches a tag to each victim as a part of the triage process. Our localization algorithm processes the unreliable RSSI values reported by the above tags using techniques such as tag calibration, tag averaging, time averaging and selective trilateration to estimate the location of the tagged victims. The system was tested in a number of experimental emergency scenarios with satisfactory results. The average error in estimated position of a tagged victim in a 100 x 100 ft emergency site setting was around 12 ft.