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Learning Outcomes

By the end of this section, you should be able to:

  • 32.3.1 Describe the term mass violence.
  • 32.3.2 Examine U.S. mass shooting statistics.
  • 32.3.3 Examine how mass violence can impact whole communities and the population at large.
  • 32.3.4 Identify signs of emotional distress related to incidents of mass violence.
  • 32.3.5 Discuss the principles of mass casualty management.

Mass violence refers to incidents of intentional criminal acts targeted at defenseless citizens with the intent to harm or kill large numbers of victims. Mass violence often occurs without warning and can happen anywhere, impacting whole communities and the country at large. These types of disasters, which include shootings and acts of terrorism, disturb the sense of order and safety in situations that are normally nonthreatening. The impact of mass violence is far-reaching, instilling feelings of confusion, fear, and helplessness. They violate the larger community’s sense of safety and order, affecting even those without personal connections to the event (SAMHSA, n.d.). The most common manifestations of mass violence are:

  • Mass shootings
  • Terrorist bombings
  • Mass riots
  • Hijacking of aircraft, trains, buses, or other transportation services

Mass Shootings in the United States

Statistically, mass violence is uncommon, with mass shootings comprising most incidents. There is no standard definition of mass shooting, but there is a common definition for active shooter. An active shooter is an individual who is killing or attempting to kill people with a firearm within an area (USA Facts, 2023). Criteria to report mass shootings differ by the number of victims, whether injuries are included, the location of the shooting, whether it occurred with another crime, and the relationship between the shooter and the victims (Smart & Shell, 2021). More common definitions include an incident where four or more people have been murdered by a firearm or an event where at least four victims were injured or killed by a firearm. Although less than one percent of all firearm deaths annually in the United States are attributed to mass shootings, they have incited fear and panic beyond the direct victims and their families (Soni & Tekin, 2022). In the United States, the rate of mass shootings and the number of people killed over the last four decades has increased, resulting in over 1,000 deaths and 1,500 injuries (NCMDI, 2019; Soni & Tekin, 2022). Federal funds to study gun violence were largely unavailable for about 20 years, but in 2019 the U.S. Congress approved funding for the CDC and National Institutes of Health to conduct gun violence research. This opened the door to new research on gun violence, suicide, and injury prevention (Weir, 2021). Table 32.6 provides 2016–2022 statistics, highlighting the recent increase in mass shootings. Table 32.7 compares the outcomes of the deadliest mass shooting incidents in the United States.

Source 2016 2017 2018 2019 2020 2021 2022
Gun Violence Archive (2023) 383 348 336 417 610 690 647
Everytown (2023) 372 341 329 410 605 686 636
*numbers vary based upon the definition of mass shooting
Table 32.6 Mass Shooting Incidents Since 2016


2017 Concert in Las Vegas, NV 60 killed 411 wounded
2016 Nightclub in Orlando, FL 49 killed 53 wounded
2019 Store in El Paso, TX 23 killed 23 wounded
2017 Church in Sutherland Springs, TX 25 killed 20 wounded
2022 Elementary School in Uvalde, TX 21 killed 17 wounded
2018 High School in Parkland, FL 17 killed 17 wounded
Table 32.7 Deadliest Mass Shootings in the United States, 2016–2022 (See Everytown, 2023; Statista, n.d.)

The Impact of Mass Violence

Mass violence and shootings have significant mental health effects on population health. These terrifying and traumatic incidents are often directed at strangers in public places. The community’s response is defensive and urgent, demanding an explanation to try to make sense of the nonsensical. In the aftermath of mass violence, political leaders often blame mental illness, a narrative that echoes the public’s common belief that individuals with mental illness generally pose a danger to others. It is difficult to comprehend the logic of mass violence or to imagine that a mentally stable person would intentionally kill multiple strangers; therefore, one might conclude that all perpetrators of mass violence must be mentally ill (NCMDI, 2019). However, according to a report from the U.S. Department of Homeland Security, the motives for mass violence are complex. The most common reasons relate to grievances, ideology, bias, political beliefs, and psychotic behavior (Alathari et al., 2023). Some offenders give multiple reasons for committing acts of mass violence, and others, killed during the event, never provide a reason. Table 32.8 outlines cited motivations for mass violence events. Over half are attributed to personal, domestic, or workplace grievances, while only 14 percent are related to psychotic symptoms (Alathari et al., 2023).

Components to Motivate* 2016 2017 2018 2019 2020 Total
Ideological, bias-related, or political beliefs 30% 24% 10% 21% 10% 18%
Psychotic symptoms 13% 26% 10% 15% 8% 14%
Desire to kill 13% 8% 3% 9% 3% 7%
Fame or notoriety 7% 8% 3% 6% 5% 6%
Other 3% 3% 10% 9% 8% 6%
Undetermined 20% 8% 10% 29% 23% 18%
*The percentages for each year do not total 100% as some attackers had multiple motives.
Table 32.8 Motives for Mass Violence Over Time (See Alathari et al., 2023.)

Mental health issues related to mass violence events are correlated to direct victims, their families, and the general population. Research has shown that 48 percent of Americans live with the fear of becoming a victim of a mass shooting, and more than 10 percent have avoided large crowds or bought a weapon because they are worried about the threat of mass shootings (Brenan, 2019). Individuals living in the community or attending the school where a shooting has occurred have increased emotional distress, with a higher likelihood of taking antidepressants, engaging in risky behaviors, or considering suicide (Brodeur & Yousaf, 2022; Deb & Gangaram, 2023).

Public health and community health nurses and other health providers must be aware of the role of mental illness in mass violence for both victims and offenders to provide support and lead efforts to prevent mass violence (Alathari et al., 2023). Like many other community health concerns, preparation and prevention are key strategies for combating mass violence. Planning and participation in regular preparation activities like active-shooter drills supports proactivity and preparation for the worst-case scenario (Peterson & Densley, 2021).

A part of preparation, albeit not coordinated, is attention to warning signs. Warning signs include having behavioral problems or difficulty connecting with others, being noncommunicative, having aggressive or violent verbalizations, being withdrawn, harming self or others, and being emotionally unstable (Peterson & Densley, 2021). Education and advocacy programs for teachers, caregivers, and the public can go a long way in promoting awareness of behaviors that might be precursors to violence in individuals. Seemingly innocuous comments or interactions may be warning signs or cries for help (Peterson & Densley, 2021).

Mass Casualty Management

Mass casualty incidents (MCIs) are human-made or natural disasters that overwhelm the resources of local management agencies and the health care system. Emergency medical services (EMS) are often the first responders on the scene of a mass casualty event, but the principles of response apply to any health care responder. First responders are critical in triaging, stabilizing, and preparing to transport victims to health care facilities after MCIs. As the name implies, MCIs involve large numbers of victims who will need varying levels of care. Effective management, communication, and collaboration are essential during an MCI. Local community agencies, such as the fire department or police department, may respond, and state or national agencies may also become involved, depending on the type and severity of an MCI (Alpert & Kohn, 2023). 

Response to a mass casualty event is complex, involving many people from different disciplines. Planning is a critical step to response, as a methodical approach to a crisis engages community responders in thinking through the lifecycle of a potential crisis, determining required capabilities, and establishing a framework for roles and responsibilities (FEMA, 2021). Since mass casualty disasters can happen without warning, a constant state of readiness requires training and regular drills. Simulations are frequently used to prepare health care workers and first responders for mass casualty management, as individuals must understand the roles that each one has in mass casualty response (Figure 32.3).

EMS workers wearing reflective vests gather outside in small groups near a yellow school bus. In the foreground, several kneel in the grass next to a dummy on a backboard. Other emergency vehicles are visible in the background.
Figure 32.3 EMS staff participate in a training exercise to prepare for a mass casualty incident. (credit: “Mass Casualty Incident Training, Mammoth Hot Springs” by Neal Herbert/NPS/Flickr, Public Domain)

Multiagency, Interprofessional Team Coordination

The National Incident Management System (NIMS) provides a framework for the management of disasters and MCIs. NIMS guides the multiagency, interprofessional structure and organization for communication and incident command, allowing for efficient communication using common terminology, clarification of leadership and roles, and effective management and distribution of resources. Figure 32.4 illustrates the organization of Incident Command System (ICS) used in NIMS. Table 32.9 provides further description of the roles of command staff in the ICS.

The ICS Command Function Organizational Chart shows to whom different staff report. At the top of the org chart is the incident command. The general staff reporting into incident command includes the operations section chief, planning section chief, logistics session chief, finance and administration section chief, and intelligence and investigations section chief. The command staff, consisting of the public information officer, safety officer, and liaison officer also report to the incident command.
Figure 32.4 The ICS provides responders with a framework for organization, decision-making, and communication during a disaster or mass casualty event. (credit: modification of work “ICS Command Function Organization Chart” by FEMA, Public Domain; attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)
Role Function
Incident Command
  • Has overall responsibility for the incident
  • Sets objectives for the incident and approves the incident action plan
  • Manages the incident and approves requests
Public Information Officer
  • Develops and coordinates press releases
  • Monitors and maintains information related to the incident
Safety Officer
  • Identifies and mitigates hazards
  • Approves the Medical Plan
  • Ensures safety messages and briefings are made throughout the incident
Liaison Officer
  • Communicates with cooperating agencies
  • Maintains list of responders and responding agencies
  • Monitors resources, providing current resource status, including limitations and capabilities of agency resources
Operations Section Chief
  • Organizes services and resources to carry out the plan
  • Supervises operations
  • Requests additional resources if needed
Planning Section Chief
  • Develops incident action plan to accomplish incident objectives
  • Collects data related to the plan
  • Facilitates meetings
  • Assembles task forces if needed
Logistics Section Chief
  • Provides facilities, transportation, communications, supplies, fuel, food, and medical services for incident personnel
  • Manages incident logistics
  • Identifies anticipated services and support
  • Oversees communications, medical, and traffic plans
  • Oversees demobilization of logistics section and resources
Finance/Administration Section Chief
  • Monitors incident costs
  • Provides financial guidance
Intelligence/Investigations Section Chief
  • Scope and function determined by the Incident Commander
  • May be incorporated as a part of the planning section, operations section, or general staff section
  • Prevents unlawful activity during incident
  • Collects, processes, and analyzes information, evidence, and intelligence
  • Investigates the cause of the incident and identifies suspects
  • Conducts missing persons investigations
Table 32.9 ICS Command Roles and Functions (See FEMA, 2018.)

The Medical Branch (nurses and other health care staff) reports to the Operations Section Chief. This includes the medical director, who supervises triage, treatment, and transport of clients; the triage officer, who oversees triage of clients; the treatment officer, who manages the treatment area; and the transport officer, who arranges and documents transport of clients from the scene (Lincoln et al., 2023). Additional roles may be added depending upon the number of clients and the time needed to manage medical needs.

Scene Safety Considerations

When responding to a mass casualty incident, there are several issues that must be considered to effectively manage the scene and victims for optimal outcomes.

  • Scene Safety
    • The top priority on the scene of an MCI is the safety of the responders. Verifying that the scene is safe before first responders provide care prevents secondary incidents and subsequent injuries (Alpert & Kohn, 2023). Scene security and the responsible agency will depend on the nature of the MCI. If the event is a vehicular accident, the environment around the scene should be assessed for fuel leakage, fire hazard, and other risks that would further endanger victims or responders.
    • Appropriate personal protective equipment (PPE) needs to be available and used by responders to a chemical, biological, radiological, or nuclear event.
    • In response to a terrorist or mass violence attack, the possibility of an explosive detonation or a suicide bomber should be considered and bomb disposal experts dispatched before responders begin lifesaving measures.
    • In a mass shooting incident, if the offender has not been apprehended or has fled the scene, first responders must not approach the scene unless they are trained in tactical medicine and are wearing appropriate protective gear.
    • The response to or after a fire poses a risk of building collapse and inhalation (Alpert & Kohn, 2023).
  • Field Triage
    • After scene safety, mass casualty response requires field triage of victims. Examples of field triage systems will follow later in this chapter.

Theory in Action

Situational Awareness in Multi-casualty Incidents

Nurses and other field-level providers increasingly will be called on to respond to both natural and human-made situations that involve multiple casualties. Situational awareness (SA) is necessary for managing these complicated incidents. SA is the ability to perceive, understand, and respond to the current situation. Basically, it is knowing what is going on in the environment, recognizing unsafe situations, and responding to the situation in a safe, efficient way. Situational Awareness For Emergency Response (SAFER) utilizes technology to access building information and video surveillance when responding to emergencies.

Watch the video, and then respond to the following questions.

  1. Why is situational awareness important when responding to a hazardous event?
  2. What information does SAFER give to responders?
  3. How can SAFER be used during response to a disaster?

Zoning of Care Areas

In an MCI, the area of care is divided into zones if there is a risk of chemical, biological, radiological, or nuclear contamination (Figure 32.5) (Alpert & Kohn, 2023).

  • The hot zone is the immediate location of the incident, where victims and responders have direct contamination. 
  • The warm zone is the area surrounding the hot zone where contamination is present from victims or responders leaving the hot zone. Triage and decontamination can occur in the warm zone to neutralize the risk to victims.
  • The cold zone is where care for victims occurs and may serve as the location for minor casualty holding or release.
A diagram shows the hot zone, warm zone, and cold zone as three ovals nested inside one another. The smallest and most interior oval is the hot zone; next is the warm zone; and the outermost oval is the cold zone.
Figure 32.5 During an MCI, responders divide care into hot, warm, and cold zones if there is a chemical, biological, radiological, or nuclear contamination risk. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

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