Preventable Mass Shootings Database

Last Updated on Thursday, September 23, 2021 @ 7:40 PM by Editor

The Preventable Mass Shootings Database is a comprehensive listing of mass shootings in the United States that ranks the degree to which each one was preventable. It should be noted that mass shootings are consistently referred to us as incidents, but we’ve named this database the Preventable Mass Shootings Database to avoid confusion about what it is and because it doesn’t contain any incidents that aren’t mass shootings. Each mass shooting in the database has been carefully and fully analyzed using our static criteria system which is expounded upon near the end of this page. In other words, we’ve unrelentingly sought all the facts, devoured them, embraced them, and played devil’s advocate with them. Granted, we’ve seesawed a few times with some cases, and likely we’ve erred with others a little, but we believe the final result is as solid a conclusion as can be had given what has reared its ugly head with these mass shootings.

The Preventable Mass Shootings Database is a work in progress and it always will be. Mass shootings that have already occurred are being added regularly and future mass shootings will be added, particularly the deadliest ones. In addition, our research of incidents in the database is ongoing, so new data that is discovered is added as well as data that was overlooked. Finally, mass shootings already in the database are regularly being reviewed, and edited as necessary, based on external feedback received, and to a lesser extent to address subjectivity issues of the authors and editors which inevitably happens.

But let’s be realistic. It’s completely impossible to predict what might or might not have been. It should also be noted that our rankings are made (because we can’t make them any other way) in perfect world hindsight scenarios, which are always few and far between.

We also want to unequivocally state that this isn’t about finger-pointing. It’s about learning. If the data in the Preventable Mass Shootings Database makes you cringe or feel guilty, you have our sympathy, but the chance to prevent future mass shooting has our vote when it come to rehashing the facts of these horrible incidents.

We fully recognize that it’s possible to blow holes in the Preventable Mass Shootings Database, and that’s okay. It’s a questionable effort given the multitude of variables at play, particularly those relating to forever fickle human behavior; the passage of time, which in some cases is decades; the myriad of unknowns; and other factors. However, if we don’t learn from the past we’re condemned to repeat it. So to that end, the Preventable Mass Shootings Database humbly exists.


… if we don’t learn from the past we’re condemned to repeat it. So to that end, the Preventable Mass Shootings Database humbly exists.


So then, the purpose of the Preventable Mass Shootings Database is the hope that society, the systems, and the venues learn. Learn what wasn’t done but could and should have been. In some cases it’s a lot. It’s for the hope that going forward society, the systems, and the venues take the proactive measures that will prevent future mass shootings.

The assigned ranks, when used relatively, are a somewhat accurate portrayal of the degree to which each mass shooting could have been prevented had proactive measures, which are often simple and/or uncostly, been employed.

But the rankings aren’t what we need to focus on, it’s the details section, where things like what wasn’t done but could have been and should have been, is listed. Obviously, if you’re looking for what can be done to prevent future mass shootings choose incidents with the higher point totals.

Following a mass shooting the media most generally broadcasts and prints the potentially preventable elements, at least for those who dig a little deeper than most people, however, the news cycle means that they won’t be around for very long, which also means they rarely are looked at collectively, which is where they have the greatest ability to teach us.

The Preventable Mass Shootings Database looks at all of it collectively and zeros in on those incident details that provide the greatest degree of societal, system, and venue learning. There’s a lot of databases and datasets out there pertaining to mass shootings, but the ones that truly matter are those that help us to learn from the past so we don’t repeat it. In other words, anybody can spew mass shooting facts and figures until the cows come home, including us, but we need to do better than that. We need to get a firm historical handle on what causes mass shootings to happen, in some cases how we let them happen, so we can do what’s necessary to thwart them going forward. We believe the Preventable Mass Shootings Database, using simple and straightforward data that zeros in solely on causes, can be some help in getting all of us to understand what truly matterspreventing the next one.


the Preventable Mass Shootings Database, … zeros in solely on causes, … getting all of us to understand what truly matters—preventing the next one.


Preventable Mass Shooting Database Criteria

The Preventable Mass Shootings Database criteria is as follows:

Items and Assigned Points

Items and assigned points are depicted below in 11 categories consisting of 25 separate items of which 21 are selectable. They aren’t intended to be inclusive, and they aren’t. The number of points that is applied to each item is also depicted below. The minimum point that can be applied to an item is 1 and the maximum points that can be applied is 3. There is also a possibility to double the points for items deemed blatant. When that’s done it will be noted in the Preventable Factor Details for the Preventable Factor/Ranking receiving the doubled points.

Behavioral Red Flag(s) Ignored (Select All That Apply)

—Behavioral Red Flag Law(s) Nonexistent – Behavioral Red Flag Law(s) Nonexistent – 3
—Perpetrator Behavior Personally Erratic/Deviates from Individual/Societal Norms 2
—Perpetrator in Directed and Overt Incident Preparatory Mode – 3
Behavioral Red Flags Ignored/Response Delayed – Perpetrator Expressed Suicidal Ideation and/or Suicide by Police and/or Expressed Violent Intentions Privately and/or Publicly in Person and/or In Any Medium – 3

Commercial Establishment Failure
Commercial Establishment Failure 3

Criminal Justice System Failures (Select All That Apply)
—Judicial System Failures
——Custodial Issues (Questionable Release/Remand of Perpetrator) 1
——Questionable “Blue Paper” Rejections of Perpetrator 1
——Questionable Search Warrant Rejections for Perpetrator 1
—Law Enforcement Failures
——Delayed Response or Inaction to Perpetrator at Incident Scene – 3
——Delayed, Ignored, or No Follow-up to Telltale Perpetrator Event(s) Preceding Incident 2
Probation/Parole Failure
——Failure to Pursue/Report Probation/Parole Violation(s) for Perpetrator 1
—Prosecutorial Failure
——Failure to Pursue Warranted Criminal Charges Against Perpetrator and/or Failure to Petition the Court for a Red Flag Hearing 3

Gun Laws Inadequate (Select All That Apply)
—Inadequate Gun Law(s) Contributed to Perpetrator Execution of the Incident – 2
—Inadequate Gun Law(s) Exacerbated the Incident – 2

Mental Health System Failure/Interventions Lacking (Select Only One)
—Incident Principals Attested to Mental Health System Failure for Perpetrator – 3
Incident Principals Charged with Mental Health System Failure for Perpetrator – 2
—Incident Principals Identified with Mental Health System Failure for Perpetrator – 1

Unnecessarily Accessible Perpetrator Weapon(s).
Weapon(s) Was Unnecessarily Accessible to the Perpetrator – 3

Venue Lacked Armed Individuals/Personnel
Venue Lacked Armed Individuals (Civilians)/Personnel (Military/Police/Security) – 3

Venue Structural Security Lacking (Select Only One)
Venue Had Limited Structural Security – 1
—Venue Structural Security is Nonexistent – 2

Venue Perimeter Security Lacking (Select Only One)
—Venue Had Limited Perimeter Security – 1
—Venue Perimeter Security is Nonexistent – 2

Vexatious Cascade of Events Besets Perpetrator
—Worrisome Cascade of Events Besets Perpetrator – 3

Whatever System Failure
—Whatever System Failure 3

Preventable Rankings Scoring

The minimum number of points for any given mass shooting is 0 and the maximum is 47. However, in the case of the latter, no mass shooting is likely to rise even close to that level. A mass shooting with a ranking of 0 is considered completely unpreventable and a ranking of 23.5 or higher is considered completely preventable.

Completely Unpreventable 0 —————————— 23.5+ Completely Preventable

Specifically, the current breakdown being used is as follows:

—Completely Unpreventable (0)
—Largely Unpreventable (1-3)
—Somewhat Unpreventable (4-6)
—Minimally Unpreventable (7-9)
—Debatable/Inconclusive (10-12)
—Minimally Preventable (13-15)
—Somewhat Preventable (16-18)
—Largely Preventable (19-21)
—Completely Preventable (23.5+)


Due to the nature of the content of the Preventable Mass Shootings Database we’re required to use some level of user identity. We’ve chosen the lowest level of identification so as not to discourage access to the Preventable Mass Shootings Database. For instance, paid access using a verified credit/debit card would undoubtedly reduce the number of people accessing the Preventable Mass Shootings Database which we don’t want to dowe want you to use it. So, you can simply register for free using an email address to gain access to the Preventable Mass Shootings Database.

Ready to get started?

Click here.

The first 23 incidents in the Preventable Mass Shootings Database are those which have been the deadliest in modern history.

While most of the data necessary to analyze every mass shooting case to the hilt is readily available online, in some cases we utilized the federal Freedom of Information Act (FOIA) to get the information needed.

It should be noted that in some instances unpreventable and preventable denotes mitigated.