The phrase ‘left of boom’ is a military idiom used to describe efforts that aim to prevent and protect military personnel from exposure to roadside bombs or improvised explosive devices (IEDs). The ‘boom’ refers to the detonation of the IED, and the ‘left’ side refers to the time (not distance) preceding the detonation. Left of boom efforts can be long, medium, or short-term. The more time between the intervention and the detonation, the more ‘left of boom’ it is.

Some interventions help detect the presence of bombs moments before they are about to detonate. For example, sensors can be used to detect them in front of moving vehicles, and then steps can be taken to prevent detonation. This is more short-term and immediate. Medium- or long-term efforts occur further left of boom. An example of this is when military personnel use observation posts to deter the placement of IEDs. In the latter, there is more time between the intervention and the detonation, so it is considered further left of boom.

Any effort to protect our soldiers from IEDs is important and should be pursued, though initially, I didn’t like the phrase ‘left of boom.’ However, I find the underlying thought process useful when I think about other problems, like active-shooter prevention.

Different active shooter prevention efforts can be assessed according to how far ‘left of boom’ they are. For you, thinking about prevention this way might help you brainstorm ideas for protecting your community.

For the purposes of this post, we will rely on the FBI definition of an active shooter incident: i.e., when an individual is “actively engaged in killing or attempting to kill people in a populated area.” This would include incidents such as the 2016 Pulse Nightclub shooting or the 2017 shooting on the Las Vegas strip.

Unfortunately, the prevalence of active shooter incidents has been increasing over time, with 2020 statistics showing a 100% increase since 2016 and a 33% increase since 2019. As such, the need for active shooter prevention and training is becoming more and more apparent.

Threat Assessment and Active Shooter Prevention

Active shooter prevention usually involves some kind of threat assessment approach. Threat assessment involves evaluating and verifying perceived threats and assessing their likelihood of occurring. Different threat assessment approaches focus on different challenges and occur at different points in time to identify long-standing threats as well as immediate threats.

Let’s take a moment and re-visit the different challenges different threat assessment efforts might be trying to solve. Some of these approaches include:

• Security Threat Risk Assessment: Plan for and protect facilities and critical infrastructure against attacks;

• Violence Threat Risk Assessment: Assess the likelihood that a specific individual will engage in some form of violent behavior in the future;

• Threat Assessment for Instrumental Violence: Identify, assess, and intervene with a person who may commit a targeted attack (e.g. a shooting at a specific time and location); and

• Active Threat Assessment: Help law enforcement or security personnel to identify and react to threatening individuals (such as active shooters).

More detailed descriptions of each threat assessment approach can be found in our Guide to Threat Assessment Approaches for Law Enforcement.

A Model of Active Shooter Threat Assessment Approaches

To understand the different types of threat assessment and their relevance to active shooter prevention, I have included a visual aid.  In Figure 1, you will see the different forms of threat assessment and their relevance to an active shooter incident. Time is established based on the time before an event (or how far left of boom). I also divided the threat assessment approaches based on whether they are environmental or individual. The different spacing between the hash marks along the horizontal axis convey the increasing time-distance from an incident.

Now, let’s think about the different forms of threat assessment and how left of boom each is from an active shooter incident.

The Security Risk Threat Assessment

Security Risk Threat Assessment is pretty far left of boom. It is environmental and involves identifying and protecting a specific location from threats. Examples include things like improving access control and surveillance, developing emergency preparedness plans, or establishing hardened locations to protect victims from a potential active shooter.

Security risk threat assessment is helpful in the long term for preventing or mitigating damage, though it becomes less relevant in the short term. More detailed information about security risk threat assessment can be found in our Guide to Threat Assessment Approaches for Security Professionals.

The Violence Threat Risk Assessment

The individually-focused Violence Threat Risk Assessment is also far left of boom. This approach involves assessing an individual’s propensity toward future violent behavior over the long-term. It is not necessarily tied to the commission of a specific violent act, but rather the person in general. This is important because an individual can exhibit important warning signs years prior to committing a severe violent act.

This approach can be coupled with an Instrumental Violence Threat Assessment if an individual warrants further intervention. Police can also engage in offender-focused policing strategies to learn more about prolific offenders and their activities.

Threat Assessment for Instrumental Violence

Because it involves the intersection of a location, a time, and an individual who might be planning an active shooter incident, the Instrumental Violence Threat Assessment is both environmentally and individually focused. It involves efforts to identify, assess, and intervene with individuals who may commit a targeted violent act at a specific location (e.g., a school or workplace).

This approach is relevant to active shooter prevention in the short- and medium-term. This can include looking out for common behaviors that individuals may exhibit in the weeks prior to committing a targeted shooting. For more information on common pre-attack behaviors, see the FBI’s Active Shooter Quick Reference Guide.

Active Threat Assessment

Active Threat Assessment is relevant in the short-term, typically right before an incident occurs (i.e., just left of boom). This approach focuses on the environment and individuals in it. It could also be combined with some of the other approaches. For example, active threat assessment can help identify individuals warranting further evaluation, or it can help to identify external threats to a certain location (such as someone conducting surveillance).

Active Threat Assessment is relevant to active shooter prevention, particularly in the medium- and short-term. One key part of this approach is that it can help you identify persons who are carrying weapons. It can also help you anticipate potential threats through the identification of behavioral indicators.

The police response to an active shooter incident involves additional tactical skills and policy considerations in addition to those mentioned here. For more information regarding the myriad of things to consider during an active shooter incident, see the FBI’s active shooter resource page, read through critical incident reviews of past attacks, or connect with other departments on the FBI’s secure Law Enforcement Enterprise Portal (LEEP). You can also view policy recommendations in the IACP’s Model Policy for dealing with active shooters.

Thinking About Active Shooter Threat Assessment and Prevention

Each of the threat assessment approaches outlined here is important to active shooter prevention in different ways. Each may also be relevant to different communities and facilities.

The nature of the location will also impact prevention efforts. Some locations are more secure (such as federal facilities), while others allow people to move around freely in and out. Other locations have a mix of secure and open areas.  All are challenging to protect in different ways.  

Thinking about each of these approaches and their time-distance from an incident (i.e., how far left of boom) will help you identify gaps in your community’s active shooter prevention efforts. After identifying gaps, you can begin to identify resources and training that can keep your officers and communities safe.

If you would like to learn more about active threat assessment or active threat assessment training, please don’t hesitate to contact us.