NIJ-funded Research on Mass 

Shootings to Advance Evidence-based 

Policy and Practice 

November 30, 2021 | 1:00 PM ET 

The webinar will begin shortly 
 

 

 

 

Important Notification 

The research projects presented here are supported by 

Awards 2019-R2-CX-0003, 2018-75-CX-0025, IAA 20RO0004 

from the National Institute of Justice of the U.S. Department of 

Justice. 

The opinions, findings, and conclusions or recommendations 

expressed here are those of the authors and do not 

necessarily reflect the positions or policies of the Department 

of Justice. 
Overview of NIJ research investment 

on mass shootings 
Estimating the Global Prevalence of 

Mass Public Shootings 

Grant Duwe, Ph.D. 

November 2021 

NIJ Webinar 
 

 

 

Presentation Overview 

• Provides preliminary results from our study (in progress) 

• “Estimating the Global Prevalence of Mass Public Shootings” by

Grant Duwe, Nathan Sanders, Michael Rocque and James Alan

Fox 

• Study addresses the following key questions 

• What is the worldwide prevalence of mass public shootings? 

• What percentage of mass public shootings occur in the United

States? 

• Prior Research 

• Data and Proposed Methodology 

• Preliminary Findings 
 

Prior Research 

• Widely divergent findings about U.S. proportion of cases 

• Lankford (2016) 

• U.S. accounts for 31% of mass public shootings from 1966-2012 

• U.S. makes up 4% of world’s population 

• Lott and Moody (2019) 

• U.S. accounts for only 3% of mass public shootings from 1998-

2012 

• Included terrorism and genocide 

• Lankford (2019) 

• Most of L&M’s dataset involved incidents with multiple offenders 

• Usually not considered mass public shootings 

• U.S. = 30% of single-offender attacks 
 

 

 

 

 

 

 

 

Limitations with Prior Research 

• Sole reliance on news coverage as data source

• Lankford (2016)  news archive and internet searches

• Published lists have also relied strictly on news coverage

• Lankford  NYPD Active Shooter

• Lott and Moody  Global Terrorism Database

• News coverage-only data collection strategy = missing cases

• Research using news reports and FBI’s Supplementary Homicide

Reports (SHR) have achieved more complete datasets

• USA Today (Overberg et al., 2013)

• Congressional Research Service (Krause et al., 2015)

• Fox, Duwe and Rocque (FDR)

• Relatively large # of U.S. cases missing from Lankford and

Lott/Moody datasets

• Comparison with FDR data from 1976-2012 period

• Implications for measuring prevalence of non-U.S. cases
 

 

Defining Mass Public Shootings 

• Mass Murder

• Incidents in which 4 or more victims are killed within 24-hour

period

• Mass Shooting

• Any gun-related mass murder

• Mass public shooting

• Incidents in which 4 or more victims are killed with a gun in a

public location

• Exclude cases in connection w/ other criminal activity, military

conflicts or collective violence

• Many of the cases included by Lott and Moody (2019) would be

classified as mass murders/shootings but not as mass public

shootings

• Similar to definition used by Lankford (2016, 2019)
 

 

 

 

The Lankford and Lott/Moody Datasets 

• Lankford (2016) 

• 292 mass public shootings from 1966-2012 

• 89 in the U.S. 

• 84 from 1976-2012 

• 82 actually meet mass public shooting criteria 

• 203 non-U.S. cases 

• Dataset includes “...all known mass shooters who attacked anywhere on the 

globe from 1966 to 2012 and killed a minimum of four victims.” (p. 2) 

• Lott and Moody (2019) 

• 1,491 incidents from 1998-2012 

• 43 in the U.S. 

• 42 actually meet mass public shooting criteria 

• “We are confident that we have all the public mass shootings for the U.S. and 

perhaps for Europe.” (p. 52) 
 

 

 

 

 

A Comparison of Three Datasets 

• Fox, Duwe and Rocque (FDR) Dataset 

• 165 mass public shootings in U.S. from 1976-2020 

• 1976-2012 period for U.S. mass public shootings 

• FDR = 124 mass public shootings 

• Lankford = 82 

• Missing 34% (N = 42) 

• 1998-2012 period for U.S. mass public shootings 

• FDR = 67 mass public shootings 

• Lott and Moody = 42 

• Missing 37% (N =25) 
Missingness Is Not Random 

Victims Lankford Lott and Moody 

Hit Miss Total Miss % Hit Miss Total Miss % 

4 

21 30 51 58.8 8 19 27 70.4 

5 

16 8 24 33.3 8 5 13 38.5 

6 

18 2 20 10.0 8 1 9 11.1 

7 

8 1 9 11.1 6 0 6 0.0 

8 

7 1 8 12.5 4 0 4 0.0 

9 

3 0 3 0.0 2 0 2 0.0 

12 

1 0 1 0.0 1 0 1 0.0 

13 

3 0 3 0.0 3 0 3 0.0 

14 

1 0 1 0.0 

21 

1 0 1 0.0 

23 

1 0 1 0.0 

27 

1 0 1 0.0 1 0 1 0.0 
 

 

 

 

 

 

 

 

Implications for Non-U.S. Mass Public Shootings 

• Lower-severity mass public shootings in the U.S. 

• More numerous (a heavy-tail distribution) 

• 77% involve between 4 and 6 fatal victims 

• Extreme cases (10+ victims) are more rare...and more newsworthy 

• Underrepresented in both Lankford and Lott/Moody datasets 

• Both datasets undercounted U.S. mass public shootings overall 

• Less newsworthy 

• Results reflect well-established disadvantages of relying only on news coverage 

• What are the Implications for Non-U.S. Cases? 

• Combined, Lankford (2016) and Lott/Moody (2019) identified 

218 non-U.S. mass public shootings from 1976-2012 

• Do most involve less than 7 fatal victims? 
Comparison of U.S. and Non-U.S. Cases by Victim Count 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Estimating the Global Prevalence of MPS 

• Evidence strongly suggests LLM combined Non-U.S. dataset

missed lower-severity cases

• 40% of MPS had < 7 fatal victims

• Assume LLM captured all of the extreme cases (10+ victims)

• LLM = 49 Non-U.S. cases with 10+ fatal victims

• FDR = 9 U.S. cases with 10+ fatal victims

• U.S. = 15.5% of all mass public shootings with 10+ victims

• Develop initial estimate of missingness for cases < 10 victims

• Assume that victim count distribution for non-U.S. is similar to that

observed for U.S.

• 4 victims = 41% of all cases

• 5 victims = 19% of all cases

• 6 victims = 16% of all cases

• 7 victims = 7% of all cases

• 8 victims = 6% of all cases

• 9 victims = 2% of all cases
 

 

Estimated Global Prevalence of Mass Public Shootings, 

1976-2012 

Number of Mass Public Shootings 

300 

250 

200 

150 

Overall Estimate = 797 

U.S. Cases = 124 (16% of total) 

Non-U.S. Cases 673 = 

100 

50 

0 

U.S. Non-U.S. 

4 5 6 7 8 9 10 11 12 13 14 15 16 17 20 21 23 27 29 30 32 34 35 58 69 
 

 

 

 

 

 

 

 

 

 

Next Steps 

• Develop additional, more refined estimates using 

hierarchical Bayesian models 

• Uses series of heavy-tailed distributions (power law, lognormal, 

etc.) to help estimate missingness in non-U.S. cases 

• Similar to prior work that forecasted the severity of mass public 

shootings in the U.S. (Duwe, Sanders, Rocque and Fox, 2021) 

• If additional estimates are similar, what’s the take-away? 

• U.S. is not like rest of the world when it comes to MPS 

• MPS are also not a uniquely American phenomenon 

• MPS incidence is still 4X higher relative to population size 

• MPS is most visible manifestation of violence in a nation that has 

long been more violent than comparable countries. 
 

IMPROVING THE UNDERSTANDING OF MASS 

SHOOTING AND OTHER MASS ATTACK PLOTS 

NIJ-funded Research on Mass Shootings to 

Advance Evidence-based Policy and Practice 

November 30, 2021 

John S. Hollywood 

Senior Operations Researcher, RAND Corporation 

Center for Quality Policing 
 

 

 

Power to Prevent 

Three Top 

Takeaways 

• Everyone can prevent

• 2/3 of our foiled plots found from public reporting

• Most cases handled outside of justice system

Relentless Follow-Up 

• Multi-organizational teams needed

• Key steps: assess, determine next steps, follow up,

and reassess regularly

Prepare and Train 

• “Heroes are made because they prepare”

• Need advance planning, resourcing, and training

for all partners

• Need to prepare for actions after the attack is over
Outline 

• Objectives 

• Methodology 

• Organizing the findings – the mass attack 

defense chain 

• Findings to prevent, mitigate, and follow 

up afterwards 

• For policymakers and executives 

• Conclusions 
Objectives 

Improve 

prevention 

Improve 

immediate 

response 

Improve 

actions after 

attacks end 

Improve 

understanding 

Improve 

understanding 

of needs 

 

 

• Characterize • Characterize • Characterize • Capture • Inform and

how plots what factors actions to findings in an support

have been and types of support educational development

discovered events have victims, toolkit priorities

and what we led to lower bystanders,

can learn casualties and

when plots responders,

reached and improve

execution community

resilience

and learning
Methodology 

Case Review Expert 

Interviews 

Literature 

Review 

Drafting and 

programming 

Advisory 

Panel 

• 600+ foiled

and

executed

plots, with

100+ cases

considered;

over 60

fields

tracked and

coded

• Dozens of • 200+

federal, journal

state, and articles,

local guidance,

policies

• Reflects

expertise

on

educational

approaches

• Feedback

from a

dozen

SMEs,

followed by

academic

QA

Formal 

publication 

• Professiona

l editing

and

programmi

ng
Organizing Findings: The Mass Attack Defense 

Chain (Top Level) 
The Mass Attack Defense Chain (Full) 
Power to Prevent: From 600+ Cases, What Led 

to Plots Being Foiled? 

Direct Threats 

28% 

Tips About 

Potential Plots 

36% 

Suspicious 

Actions 

3% 

Extremism / 

Terrorism 

Investigations 

24% 

Ordinary 

Criminal 

Investigations 

9% 
 

 

 

 

Top Warning Signs: The Something in “See 

Something, Say Something” 

Motivation: 

serious 

intent to 

attack 

Preparation: 

concrete 

actions for 

attack 

Warning:

intent + 

actions 

 Inspired by past attacks to be

infamous, too

 Inspired to fulfill an extremist

cause (esp. if kicked out of a

group for being too violent)

 Belief that someone(s) is so

harmful or threatening that they

have no choice but to attack

 Written plans for an attack

 Trying to recruit others

 Trying to learn how to kill many

people (in person, online)

 Coordinating with known violent

extremists

 Seeking arsenals of weapons &

ammunition (without a benign

reason, like hunting)

 Travel for training or to target

 Site probing / breaching
 

 

 

 

Relentless Follow-Up: A Model for Using Warning 

Signs, Threat Assessment, and Follow-Up Actions 

Report Threat 

assessment 

Follow-up 

actions 

Risk & 

mitigating 

factors 

Warning 

signs 

Vetted 

report 

Update 

Follow-up 

decisions 

Start 

End 

(monitoring 

and age-out) 

Can be charges, but 

mostly services, 

protective measures, 

and watchful waiting 

Iterative process to 

get new info, followup, and re-evaluate 

Show possible 

intent & action 

towards an attack 

Intake, initial 

handling & 

vetting 
Prepare and Train: Mitigating Casualties from 

Mass Shootings and Other Mass Attacks 

Overall: Need a Coordinated Response for Mitigation, which requires advance planning, 

coordination, and training, among all response partners 

Securing venues 

•Distance, 

movement, & 

physical barriers 

• Don’t let shooters 

surprise a crowd at 

close range 

without ways to 

escape 

Bystander & 

security response 

• Basic strategy of 

Run, Hide, and 

Fight 

• Value and risks of 

intervening in 

different types of 

situations 

Law enforcement & 

medical response 

Command & 

communications 

 

 

 

 

 

 

 

 

•Need multi- • Learn, train & 

organizational implement the 

planning and Incident Command 

training of all System & NIMS 

participants 

For Leaders: Need to Support Planning, Coordination, and Training which requires direction, 

ongoing follow-up and resourcing (and if necessary, seeking resources) 
 

 

 

 

 

 

 

Post-Attack 

Priorities: 

Planning and 

Training is a 

Necessity 

• In the immediate aftermath of the attack: 

Search and apprehension of attackers 

Investigate attackers and potential co-conspirators 

Immediate mental health and emotional support 

Family assistance centers/ post-event victim welfare 

Public communications and public relations 

Near term debriefs 

• Provision of health, support, and community services: 

Mental health and emotional support for 

victims/survivors 

Victim services, family assistance, and long-term 

services 

Mental health and emotional support for first 

responders 

Long-term responder and family support and services 

• Longer-term recognition and learning 

Recognition: awards for acts of valor; ceremonies for 

victims and heroes 

Memorials and anniversary events/VIP visits 

After Action Reports 
For Policymakers and Executives 

 

 

 

 

 

 

Ongoing Support for 

Teams 

• Can use internal 

authorities 

• Can use external tools at 

local, state, and federal 

level 

Improvements for 

Procedures & Training 

• Public education on 

reporting 

• Finding pre-attack site 

surveillance & gun 

diversion 

• Wellness checks 

• Threat assessment 

• Coordinated response 

• Coordinated post-attack 

actions 

Resources are Available 

• Commonly known – 

federal grants 

• Others that are less 

known – state and local 

sources, relevant 

philanthropies 
Online Toolkit 

 

 

 

 

 

What You Need to 

Know Now 

The key takeaways to 

improve your own 

prevention efforts 

Research Findings 

New and already-established 

findings to inform prevention 

priorities 

Tools & Programs 

Learn about solutions from 

agencies 

Policy & Program 

Needs 

From leadership and 

elected officials to 

address challenges 

Case Examples 

Cases to illustrate possible 

solutions, successes, and 

challenges 

For Further 

Reading 

Additional resources 

and references 

AUDIENCES – “TOOLKIT FOR EVERYONE” 

Law Enforcement Policy Makers Public 

& Service 

Providers 
Conclusions – 

Coming Soon 

And remember top 

three – 

 Power to 

prevent 

 Relentless 

follow-up 

 Prepare and 

train 
Questions? 

John Hollywood 

johnsh@rand.org 

Center for Quality Policing 
 

 

Active Shooter IV Project 

November 30, 2021 

FBI – BAU1 

Behavioral Threat Assessment Center 

SSA Karie Gibson, Psy.D., LP 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 33 
 

 

 

Active Shooter: Phase I 

PHASE I (2014): 160 events 

• Incidents during 2000-2013 

• Actively killing or attempting to kill 

• Using a firearm 

• In a populated area 

“What happened during and after the shooting?” 

Relied on incident reports and open sources 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 34 
 

 

Active Shooter: Phase II 

PHASE II (2018): 63 active shooters 

• Demographics 

• Weapons 

• Stressors and concerning behaviors 

• Grievances, targeting, pre-attack 

communications 

• Substance abuse and mental health 

“How do active shooters behave before they attack?” 

Subtle behaviors verified in full investigative files 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 35 
 

 

 

Active Shooter: Phase III 

PHASE III (2020): 63 active shooters & 63 

persons of concern 

“How do active shooters differ from 

individuals who display concerning behavior

but do not commit mass violence?” 

• Differences in concerning behaviors and 

stressors 

• Variation in bystander responses 

• Law enforcement investigative files 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 36 
 

 

 

 

 

Active Shooter: Phase IV 

PHASE IV: 72 active shooters (adjudicated) 

• 13 subjects from AS II 

• 67 potential interviews to complete 

• 60 prison locations 

• Interview protocol expanded from AS II to 

include findings from AS III 

“Offender interviews will allow a better 

understanding of the thought processes,

motivations, planning/preparation, and tactics

used.” 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 37 
 

 

 

 

 

 

Active Shooter: Phase IV 

Update: 16 cases coded/reconciled 

Sample Findings: 

1) Majority showed desire to obtain weapons 6 months or more before incident 

2) Majority felt rejected and disenfranchised within the year leading up to the 

attack 

3) The shortest amount of time between grievance and attack was 3-5 months 

with most being 25 or more months 

4) Most common concerning behavior reported was offender’s mental health 

issues 

5) Most common concerning behavior that was observable but did not raise 

concern was the offender’s behavioral leakage 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 38 
 

 

Active Shooter: Phase IV 

Plan: 

• Ongoing coordination with prisons 

• Interviews to begin in 2022 

• Coding to continue with revised protocol 

• Full-time researcher assigned 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 39 
 

Thank You 

FBI-BAU1 

Behavioral Threat Assessment Center 

SSA Karie Gibson, Psy.D., LP 

kagibson2@fbi.gov 

UNCLASSIFIED//FOR OFFICIAL USE ONLY 40