Active Shooter Detection Systems: What Each Technology Does, and Where It Stops

An active shooter detection system identifies signs of an armed attack, such as a gunshot or a weapon in view of a camera, so that the people who respond are told sooner. Vendors and buyers also use the phrase, more loosely, for other technologies sold for the same emergency. Five are worth telling apart, because they do different jobs:

• Gunshot detection identifies signals associated with gunfire.
• Visible-weapon detection identifies weapons visible to its cameras.
• Weapons screening checks people or their belongings at an entrance.
• Staff panic alerts depend on a person pressing a button.
• Mass notification distributes warnings and instructions.

Two of them, gunshot detection and visible-weapon detection, watch for signs of an attack on their own. Screening checks people at a door, panic alerts need a person and mass notification spreads the word. This guide is for anyone responsible for safety in a building: an office, a store, a house of worship, a government building, a hospital or a school. It explains what each technology does, the four jobs in a response and which technology can do each one, where the chain between them can break, what state panic-alert rules ask of schools, and what to ask before you buy.

Where active shooter incidents happen

The FBI defines an active shooter as "one or more individuals actively engaged in killing or attempting to kill people in a populated area." In 2025 it identified 34 active shooter incidents. Fourteen were in commerce, a category that covers "open and closed businesses like retail stores, restaurants, office space, and warehouses." Seven were in open spaces such as streets and parks, six at government sites, four in education and three at houses of worship.

Two details matter for planning. Several attacks counted in other categories began outside the building: the FBI describes shooters firing in the parking lots of a Target and a Harris Teeter, outside a church as its service began, and outside a sheriff's office before going in. And seven of the 34 shooters were insider threats, which the FBI defines as "an employee, contractor, student, or other individual with legitimate access and/or trust." A plan built only around the front entrance leaves those cases to its other measures.

Five technologies, in one line each

• Weapons screening checks people and bags as they come in, with walk-through metal detectors, hand wands or newer weapons detectors, which the school safety group PASS (Partner Alliance for Safer Schools) says also use an object's size, shape and density. It covers only the entrances where it runs.
• Visible-weapon detection is software that watches security camera images and recognizes a weapon a camera can see. PASS lists "a handgun, rifle, or large bladed knife," and notes that a concealed weapon "will not be detected."
• Staff panic alerts are buttons, worn or mounted, that a staff member presses to send an alert to the people who respond. Nothing in them senses a threat: they depend on a person noticing one and being able to press.
• Gunshot detection uses sensors that identify signals associated with gunfire and report where they were picked up. PASS describes systems that use "sound and infrared analysis"; others pair the sound with the change in air pressure a shot produces. As PASS puts it, "a gun must be fired for the technology to respond."
• Mass notification distributes warnings and instructions through public address, phones, computers, strobes and signs. It does not detect a threat itself: a person, or a connected system where one is set up, starts it.

For a side-by-side of what screening, camera detection and gunshot detection each need on site, see how gunshot detection compares.

Four jobs in a response, and which technology does each

One way to plan is to treat a response to an armed attack as four jobs: noticing it, confirming it, calling for help and telling people what to do. Which of these jobs a product performs depends on its capabilities and how it is set up, and a connected system can carry an alert through several of them. None of the five notices every kind of threat, so the chain can still break at each step.

Noticing

Three technologies can notice something by themselves: screening, at an entrance where it runs and is staffed; visible-weapon detection, where a camera can see; and gunshot detection, once a shot is fired within range of its sensors. Everywhere else, noticing depends on people. A staff member may see a weapon in a bag, hear a threat or watch a dispute turn violent before any device could respond, and a panic button lets them act on it.

• Where it can break: an entrance nobody screens, a corridor no camera covers, a weapon that stays concealed, an area with no sensors, or nobody near enough to see.

Confirming

Someone or something has to decide that an alert is real before it goes further.

• PASS recommends that a camera alert go to a person first: "on alert, a staff member verifies that the camera image(s) does contain a weapon," with someone always available to receive alerts, either your own staff or a monitoring service.
• Some outdoor gunshot networks send each event to people for review. SoundThinking, which makes ShotSpotter, says its experts "verify the incident in real time" and that the process "takes less than 60 seconds from the time of the shooting" to an alert on a screen in the emergency call center or on an officer's phone.
• Some gunshot sensors confirm with a rule of their own, such as requiring two different signals within a fraction of a second.
• With a panic alert, the person who presses it has already judged the threat. Whether anyone else checks before others are told depends on how the system and the plan are set up.
• Where it can break: nobody free to check an image, a review step that takes longer than planned, or a staff member unsure whether to press.

Calling for help

The alert then has to reach the people who respond: on-site staff, security, administrators or emergency dispatch. Panic alerts are built for this job. The federal Cybersecurity and Infrastructure Security Agency (CISA) notes that duress alarms in places such as classrooms and offices "can provide a direct connection to local law enforcement and emergency responders during an incident." A gunshot system can send its own alert. Under the procedure PASS recommends for camera alerts, the staff member who checks the image then notifies the appropriate people or law enforcement.

• Where it can break: an alert that goes to someone who is away, a location too vague for responders to use, or a call for emergency help that depends on someone remembering to make it.

Telling people what to do

Mass notification does this job. A person can start it, or, where it is set up, a connected system such as a gunshot sensor or a panic alert. A message helps only if people receive it and know what it asks of them. CISA's school security guide says using a public address system well "requires that students and staff know what they are supposed to do when they hear specific announcements." Guidance for buildings from the National Institute of Standards and Technology (NIST) notes that hearing impairments, visual impairments and the situation people are in can keep them from receiving emergency information, which is one reason to use more than one channel.

• Where it can break: a message nobody starts, a message that does not say what to do, or a channel that does not reach the people who need it.

One hypothetical case, through the four jobs

A person carrying a concealed handgun comes in through a side door that someone propped open, so screening at the main entrance never sees them. In a corridor the weapon comes out. If a camera covers that corridor, visible-weapon detection may flag it, and the alert waits until someone is free to check the image. If a staff member sees the weapon first and has a panic button, they can raise the alert themselves. If a shot is fired within range of gunshot sensors, those sensors can respond whether or not anyone is able to make a call. Whether everyone else learns what to do depends on someone, or a connected system, starting mass notification, and on a message people can hear and understand.

Each step is a condition, and the propped door is a gap none of the five closes. Monitoring that alerts staff when a door is propped or held open addresses that part; see door monitoring.

What school panic-alert laws require, and what they do not

The state laws written for school emergencies, often called Alyssa's Law, name panic alarms and panic alert systems. As of October 2026, at least 14 states have enacted Alyssa's Law or a comparable law. Seven of them require public schools to have a panic alert system, with conditions: New Jersey also accepts an approved alternative, and Utah ties classroom devices to a safety needs assessment. The others require schools to consider one, list it as one option, or permit it. Our Alyssa's Law page lists the states and what each requires. Two examples:

• New Jersey requires each public elementary and secondary school building to "be equipped with at least one panic alarm for use in a school security emergency including, but not limited to, a non-fire evacuation, lockdown, or active shooter situation," unless the district uses an alternative emergency mechanism approved by the Department of Education. The alarm must be "directly linked to local law enforcement authorities" (where a town has no police department, to a location the State Police designate) and "shall not be audible within the school building."
• Texas requires each district and open-enrollment charter school to provide each classroom with "silent panic alert technology that allows for immediate contact with district or school emergency services and emergency services agencies, law enforcement agencies, health departments, and fire departments."

None of the state law texts we have read mentions gunshot detection, camera weapon detection or metal detectors. A school can add any of them to its plan, but they are not the system these laws describe. If your school must comply, our Alyssa's Law compliance guide walks through it.

National survey data shows where schools start. In 2021-22, 92.6% of public schools in the United States used security cameras, and 43.0% had silent alarms directly connected to law enforcement, up from 27.1% in 2015-16. Few checked students with metal detectors: 2.4% did so every day and 6.2% at random. The table does not report gunshot detection. For federal and state funding routes, see our school safety grants page.

What the evidence shows, and what it does not

A federal summary from 2017 is cautious. That year the National Institute of Justice summarized two studies it funded on school safety technology. Both concluded that "the recent increase in the use of technology has not been accompanied by rigorous research into its effectiveness," and both found that "no one technology, school climate intervention, or other school safety strategy can guarantee school security."

Those findings are from 2017 and concern schools. They are still a reason to judge a system by what it can show you in your own building rather than by its brochure: a test you can watch, a coverage map checked against your floor plan, and an alert traced from the first signal to the people who respond. PASS, writing for schools and districts, recommends that weapons and gunshot detection systems be tested once a month with the manufacturer's approved test device, and that staff training also happen monthly.

Questions that apply across all five

1. Which of these technologies does the product itself include, and which does it only connect to?
2. Whose job is it to confirm an alert, who covers that job when they are away, and what does the system do if nobody confirms it?
3. Can a staff member raise an alert where no device would?
4. Can it use what we already have, such as cameras, a PA system or panic buttons, or does it replace them?
5. If we run more than one of these, whose response plan does each alert follow, and who reconciles two alerts about the same event?
6. How do you test the whole chain, from the first alert to the message people hear, and can we watch a test?
7. What happens when a part goes offline, and who finds out?
8. What does it record, who can see the record, and for how long?

For questions specific to gunshot detection, see the checklist on our gunshot detection page.

Where Positive Proof fits

Positive Proof provides two of the five technologies, staff panic alerts and gunshot detection, in one system that also runs door monitoring and visitor management.

• Panic buttons are physical buttons, worn on a badge or mounted at a desk or wall. A two-second press and hold sends the alert. There is no button on a phone screen to find under stress. A two-button badge can separate a call for on-site help from an emergency sent straight to 911 dispatch, with location attached. In the facility configuration, designated responders get the alert with the exact location in under two seconds. See how panic buttons work.
• Gunshot detection confirms a gunshot when a sensor registers both an audible spike and an immediate air-pressure change within a half-second window, so a loud sound on its own does not trigger it. It notifies law enforcement radio or 911 in under two seconds and can start panic alerts, strobes and PA announcements. See how it works.
• One dashboard. Gunshot events, panic alerts, door status and visitor logs appear in one place, and alerts can go out by two-way radio, strobes, PA system, email and text, and 911 dispatch. Positive Proof is one of the only systems available that combines gunshot detection and panic alerts in a single unified system.

Positive Proof works with schools and districts, government buildings, houses of worship, healthcare facilities and businesses. If you are working out which of the four jobs your building already covers, request a demo and we will walk through your floor plan with you. If your concern is mainly staff safety in a hospital or behavioral health unit, see our guide to choosing a staff duress system.

Frequently asked questions

What is an active shooter detection system?

Technology that identifies signs of an armed attack so responders are told sooner: gunshot detection, which identifies signals associated with gunfire, and visible-weapon detection, which identifies weapons its cameras can see. The phrase is also used more loosely for weapons screening at an entrance, for staff panic alerts, which a person presses, and for mass notification, which distributes warnings. Those three do other jobs in a response.

Is a panic button an active shooter detection system?

Not in the sensor sense, because nothing in it detects a threat. A panic button lets a staff member who notices a threat send an alert to responders. That can happen before a camera sees a weapon or a shot is fired, which is one reason to consider panic buttons alongside sensors.

Is mass notification the same as active shooter detection?

No. Mass notification distributes warnings and instructions, but it does not detect a threat itself. A person, or a connected system where one is set up, starts it.

Does Alyssa's Law require gunshot detection?

Not in any state law text we have read. Alyssa's Law and comparable state laws name panic alarms or panic alert systems that connect to law enforcement, and seven states require public schools to have one, some with conditions or an approved alternative. Gunshot detection can sit beside a panic alert system in a school's plan, but it is not what these laws describe.

Do we need more than one of these technologies?

It depends on which of the four jobs your building already covers: noticing a threat, confirming it, calling for help and telling people what to do. Which jobs a product performs depends on its capabilities and setup, and none of the five notices every kind of threat, so a plan that relies on one should say how the other jobs and moments are covered. Start with who is in the building, which doors stay open and who would respond.

Is there evidence these systems reduce harm?

In 2017 the National Institute of Justice, summarizing two studies of school safety technology, reported that its growing use "has not been accompanied by rigorous research into its effectiveness." Judge any system by tests you can watch in your own building, and by how its alerts reach the people who respond.