Are the Deadliest Mass Shootings Preventable? An Assessment of Leakage, Information Reported to Law Enforcement, and Firearms Acquisition Prior to Attacks in the United States

• Author: Adam Lankford,Eric Madfis,Krista Grace Adkins
• Published date: 01 August 2019
• DOI: 10.1177/1043986219840231
• Date: 01 August 2019
• Subject Matter: Articles

https://doi.org/10.1177/1043986219840231

Journal of Contemporary Criminal Justice

2019, Vol. 35(3) 315 –341

© The Author(s) 2019

Article reuse guidelines:

sagepub.com/journals-permissions

DOI: 10.1177/1043986219840231

journals.sagepub.com/home/ccj

Article

Are the Deadliest Mass

Shootings Preventable?

An Assessment of Leakage,

Information Reported to Law

Enforcement, and Firearms

Acquisition Prior to Attacks in

the United States

Adam Lankford1, Krista Grace Adkins1,

and Eric Madfis2

Abstract

This study examined the 15 deadliest public mass shootings in the United States

from March 1998 to February 2018 to assess (a) leakage of violent thoughts/intent,

(b) leakage of specific interest in mass killing, (c) concerning behaviors reported to

law enforcement, (d) concerning interest in homicide reported to law enforcement,

and (e) firearms acquisition. We then compared our findings on the deadliest public

mass shooters with the Federal Bureau of Investigation’s (FBI) findings on active

shooters in general. Overall, the results suggest that most incidents were indeed

preventable based on information known about offenders in advance, and that

the deadliest mass shooters exhibited more warning signs and were more often

reported to law enforcement than other active shooters. Future prevention efforts

should aim to educate, encourage, and pressure the public to report warning signs

to law enforcement, educate and train law enforcement so that they can more

effectively investigate potential threats, and limit firearms access for people who have

admitted having homicidal or suicidal thoughts or being interested in committing a

mass shooting. These relatively straightforward steps could significantly reduce the

prevalence of future attacks.

1The University of Alabama, Tuscaloosa, AL, USA

2University of Washington Tacoma, WA, USA

Corresponding Author:

Adam Lankford, Department of Criminology & Criminal Justice, The University of Alabama, P.O. Box

870320, Tuscaloosa, AL 35487-0320, USA.

Email: Adam.Lankford@ua.edu

840231CCJXXX10.1177/1043986219840231Journal of Contemporary Criminal JusticeLankford et al.

research-article2019

316 Journal of Contemporary Criminal Justice 35(3)

Keywords

public mass shootings, warning signs, prevention, leakage, firearms

Introduction

Despite decades of research into the psychology, behavior, and life histories of mass

shooters, many people remain skeptical that it will ever be possible to predict or pre-

vent their attacks. For instance, recent media articles have insisted that “We Can’t

Predict Who Will Commit a Mass Shooting” and that “Predicting a Mass Shooting Is

Impossible” (Resnick & Zarracina, 2018; Singal, 2015).

The phrase “mass shooting” is often used to refer to a more specific type of crime

known as a public mass shooting or an active shooting. These are incidents in which

perpetrators open fire in public places with the intent of harming multiple victims, and

do not include gang conflicts, robberies, or other more conventional crimes (Blair &

Schweit, 2014; Lankford, 2016b). The key distinction is that while public mass shoot-

ings are traditionally defined as cases resulting in four or more victims being killed,

active shootings have no minimum threshold (Blair & Schweit, 2014; Fox & Levin,

2015b; Lankford, 2016b). Past attacks have occurred at schools and colleges, work-

places, malls, movie theaters, churches, government buildings, military facilities, and

other public locations (Blair & Schweit, 2014; Kelly, 2012).

Part of the prediction and prevention challenge is that even in the United States—

where these offenders are most common—there are more than 1 million people who

will not commit a public mass shooting for every individual who does (Blair &

Schweit, 2014; Kelly, 2012; Lankford, 2016b). This makes preemptively identifying

possible offenders seem as hopeless as finding the proverbial needle in a haystack.

Even if the search for potential mass shooters is narrowed to subsets of the population

most likely to contain at-risk individuals, this is not nearly precise enough for success-

ful risk assessment. For example, most public mass shooters are male, but the vast

majority of men and boys would never consider committing a mass shooting (Madfis,

2014c). Similarly, most public mass shooters own guns and struggle with mental

health problems, but the vast majority of gun owners and people with mental illness

are also nonviolent (Madfis, 2014b; Schildkraut & Muschert, 2013; Schug & Fradella,

2014).

Leakage of Mass Shooters’ Violent Thoughts and Intent

Fortunately, the challenge is not necessarily to identify public mass shooters among

millions of law-abiding citizens, because in many cases they actually identify them-

selves. This is often referred to as “leakage.” As O’Toole (2000) summarized in her

threat assessment of school shooters, “‘Leakage’ occurs when a student intentionally

or unintentionally reveals clues to feelings, thoughts, fantasies, attitudes, or intentions

that may signal an impending violent act. These clues could take the form of subtle

threats, boasts, innuendos, predictions, or ultimatums” (p. 16).