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Determining the exact location of an indoor shooter(s) has been a technical challenge for companies that develop sensors intended for law enforcement and national security applications.  And with the increased number of high-profile mass shootings, whether in schools, military bases, or shopping malls, there is an urgent need for more accurate indoor shooter detection systems that are also low-cost since many institutions that would benefit are budget-constrained.

False alarms could cause an emergency evacuation and armed response.  Not only is there a risk for accidental shooting by law enforcement to a nonevent, having multiple false positives would undermine overall confidence in the system (e.g. building occupants become complacent to an alarm event). 

Presently, there are no successful technologies available in the market that could detect and locate the shooter(s) indoors in a real-time manner, which could enable first responders to respond quickly and mitigate further violence.  However, LLNL researchers have developed a very inexpensive local stand-alone active Shooter Alarm System (SAS) by incorporating micro-sensors that can be used to solve the shooter detection/localization problem while simultaneously alert first responders (e.g. security, police, medical personnel) and provide them with critical information in near real-time.


LLNL’s SAS technology embedded within a facility is developed to sense, detect, localize, alert, and communicate an active shooter(s) to first responders.  It relies on three integrated compact sensors that detect sound, infrared light (from the muzzle blast) and vibrations emanating from a gunshot.  Fusing the data from these detectors minimizes false alarms.

Once a gunshot(s) is detected, notifications on the whereabouts of the shooter could be sent to first responders in near real-time.  Local alarms could also be initiated (e.g. strobe lights, sound) to raise awareness of the location where the most recent gunshot was detected.



Lehman, S. K., Bower, D. E., & Fisher, K. A.. Shooter Alarm System Final Report FY23. United States (


LLNL’s SAS system has numerous advantages over current available systems, such as:

  1. Integration of three sensors creates extremely high accuracy that does not exist at a low price point.
  2. SAS is very robust and performs well in complex environments.  The system’s very high success rate is due to its embedded sensor suite, which enables data validation through the fusion of infrared and vibration measurements with microphone measurements.
  3. Near real-time information for first responders and tracking ability can mitigate further violence.
  4. Low-cost technology allowing institutions with constrained budgets to acquire this technology and improve the safety of their indoor facilities.
  5. Micro-sensors used are very cost-effective, extremely small in size and can be hidden.
Potential Applications

Shooter Alarm System (SAS) has been designed to be installed in many types of buildings (e.g. public school, universities, government, commercial/retail, transportation centers like airports). 

If a gunshot is detected, SAS can provide first responders with near real time information such as the location of where the firearm was discharged as well as locations of any subsequent discharges, which may indicate the shooter is moving within the building or perhaps multiple shooters are involved. 

Development Status

Current stage of technology development:  TRL 8

US Patent No. 11538322 Event detection unit published 12/27/2022

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