Selection of the AR-15 Rifle in Premeditated Indiscriminate Mass Shootings


A total of four independent, premeditated and indiscriminate mass shootings occurred in the latter half of 2012.  There was no connection between the shooters and the victims, and no reason was established in the selection of victims other than inflicting mass casualties.  An AR-15 rifle was the weapon used in all four of these events.  The odds of this particular weapon being selected for all four of these independent events simply by chance was estimated to be less than one in a million using two different approaches.  The intentional selection of this firearm is additionally supported by the behavior of all four shooters.  It is felt that this finding fundamentally changes the assault weapon debate.  It is not that this weapon was simply being used at these events, there is little if any doubt that it was being intentionally selected as a weapon of choice in those premeditated indiscriminate mass killings.  As this weapon is being actively sought for these events, leaving it unregulated and expanding public availability could only increase the opportunity for its use in future mass shootings of the nature we witnessed in 2012.

Although mass shootings are relatively low frequency events and claim far fewer lives than the broad body of shootings in this country, they garner much attention because of the horrific nature of the events.  According to one source, there have been 62 mass shootings in the US since 1982 that occurred in 30 states from Massachusetts to Hawaii (ref).  Twenty-five (25) of these took place since 2006 and 7 of them occurred in 2012.  Of the 143 guns possessed by the assailants, more that three-quarters of them were obtained legally.  More than half of those shooters possessed  high-capacity magazines, assault weapons, or both (ref).

However, the debate about ‘assault weapons’ and ‘mass shootings’ often gets bogged down in semantics and definitions.  What exactly constitutes an ‘assault weapon’ and how does one define a mass shooting.  Lists of mass shootings vary in number due to different definitions and often include a mix of different types events involving different circumstances.  And although we see a certain type of weapon appearing at these events, is that occurring simply by chance?

The purpose of this article is to simplify the matter by selecting a specific type of mass shooting event.  The mass shooting events considered will be those that were premeditated, where there was no connection between the shooter and the selected targets, and where no reason was found for the shooting other than the indiscriminate killing of multiple individuals.  These are the events that garner much public and media attention because of the senselessness of the act.  The timeframe being examined is the last six months of 2012 as that time period contained a number of mass shootings including two of the worst in US history, the Aurora CO movie theatre shooting and the Sandy Hook Elementary School massacre in Newtown, CT; both were major events in initiating the current gun control debate.  As will be detailed below, four such events, all considered to be independent of each other, were identified in that timeframe.  In all cases an AR-15 rifle was used by the shooter.  The odds of that firearm being selected in all four of these independent events simply by chance are considered.

AR-15 History and Distribution (ref) (ref)


The AR-15 was developed by the Fairchild ArmaLite corporation.  The name of the weapon is derived from ArmaLite Rifle of which there have been several rifles bearing that prefix, i.e., the AR-10, AR-5, AR-7 (semi-automatic survival rifle), and the AR-1.  The AR-15 was developed as a lighter, 5.56 mm version of the AR-10.  Amalyte sold its rights to the AR-10 and AR-15 to Colt in 1959.  The AR-15 was designed as an ‘assault rifle’ for the United States armed forces and Colt marketed the firearm to various military services around the world including the US Navy, Air Force, Army, and Marine Corps.  The select-fire version of the AR-15 entered the US military system as the M16 rifle, becoming the US military’s standard service rifle of the Vietnam War by 1969 of which several variants including the M16A1 and M16A2 followed.

Colt began selling the semi-automatic version of the M16 rifle as the Colt AR-15 for civilian use in 1963.  The semi-automatic AR-15’s sold to civilians are internally different from the full automatic M16 although nearly identical in external appearance.  A major internal feature is that the firing mechanisms are not interchangeable thus satisfying ATF requirements that civilian weapons may not be easily convertible to full-automatic.  Although the name AR-15 remains a Colt registered trademark, variants of the firearm are independently made, modified and sold under various names by multiple manufacturers, thus creating an AR-15 ‘family’.  AR-15 rifles are popular amongst civilian shooters and law enforcement forces around the world due to their accuracy and modularity.

AR-15 Rifle

M16 Rifle


As of 2012 there were an estimated 2.5 – 3.7 million rifles from the AR-15 family in civilian use in the United States.  The NRA also claims that about 3 million AR-15’s are held by American citizens (ref).   A November 2012 Congressional Research Service report estimated that in 2009 there were approximately 310 million total firearms available to civilians in the United States: 114 million handguns, 110 million rifles, and 86 million shotguns (ref).   When placed into the context of all guns held by the American public, the 3 million AR-15’s constitute only about 1% of all firearms held by US citizens.

The Events (July – December 2012)

Four unrelated, premeditated, indiscriminate mass shooting events occurred in the last six months of 2012.  All these events occurred in different states, the assailants were not connected with one another nor their victims, all were premeditated, no apparent reason existed for the selection of the targets (except to inflict mass casualties), and none were considered to be “copy cat” events of each other – all involved different populations and are considered to be independent events.  The four events were the Aurora CO movie theatre shooting on 7/20/2012, the Happy Valley OR mall shooting (12/12/2012), the Sandy Hook Elementary School massacre in Newtown, CT on 12/14/2012, and the ambush of first responders in Webster, NY on 12/24/2012.  In each of these events the shooter used an AR-15 rifle.  Several other events that occurred during that timeframe have been identified as mass shootings (ref), but have been excluded for reasons that follow.

Heavy consideration was given to including the Sikh Temple shooting in Oak Creek, WI on 8/5/2012, but under the definition of events being used here it differed from the above four as a reason existed for the selection of the victims.  The assailant (Page) was a white supremacist with ties to neo-Nazi groups (ref) who harbored ethnic/racial hatred thus establishing a motive in the selection of the victims.  Although what specifically triggered Page remains unknown, the Southern Poverty Law Center has referred to Page as being a frustrated neo-Nazi, and the chairman of the Sikh Council on Religion and Education expressed his concerns of other white-supremacy and neo-Nazi groups harboring similar intentions.  This event was felt to be more of a hate crime than an indiscriminate mass murder event.

Regarding the four selected events above, no apparent reason was found for the selection of the targets: movie theatre goers (Aurora), holiday shoppers (Happy Valley), school children and their teachers (Newtown), and first responders that were intentionally drawn to a scene for the purpose of committing mass murder (Webster).   Although the Webster event also included attacking a specific population (first responders), there was no evidence of animus towards firefighters on the part of the shooter and a typewritten letter by the assailant (Spengler) reflected the intent to ambush the first responders but offered no motive for the shooting, stating that he had to get ready “..and do what I like doing best, killing people” (ref).

The other excluded events are more straight-forward.  The 8/13/2012 shooting in College Station, TX came from a home where gunfire from an AR-15 was directed at law enforcement officers attempting to serve an eviction notice.  The 9/27/2012 shooting in Minneapolis was employment-related and directed at members of the assailant’s company; he pulled the gun when his employment was terminated.  The 10/21/2012 shooting in Brookfield WI was directed at the assailant’s estranged wife who worked in the spa (she had issued a restraining order) and it is unclear if any of the other deaths/injuries that occurred in the spa were premeditated.  And the Frankstown Township PA shooting spree on 12/21/2012 involved the shooter killing a woman on the steps of a church, driving to a neighbor’s home where he killed the neighbor and after leaving the scene intentionally rammed his pick-up truck into the vehicle of that neighbor’s son-in-law where he then shot the relative establishing some level of connection between the shooter and 2 of his 3 victims.

Odds Considerations

It is recognized that this is a complex problem.  It is known that some individuals own multiple AR-15 rifles (one individual in a recent newscast claiming to own 17 of them) thus reducing the number of individual owners to some extent (would be fewer owners than the number of rifles).  Additionally the level of gun ownership varies from state to state and the distribution of AR-15’s in various states was not found. However, assuming that AR-15 rifles would not be overly concentrated in the four states where these events occurred (considered unlikely as there are only 3 million amongst 300 million total firearms nationwide),  a straight-forward statistic was felt to be the percentage of AR-15 rifles amongst all firearms held by the American public (that being about 1%, or 0.01).

Using that statistic, and assuming no bias in selection amongst handguns, rifles and shotguns (all can be used to kill people), the odds of an AR-15 rifle being selected simply by chance at any of these individual events would be about 1 in 100, or 0.01.  The odds that an AR-15 would be selected simply by chance at all 4 of these independent events would be 0.01 X 0.01 X 0.01 X 0.01 = 10(-8), or about one chance in a hundred million.

As a rifle was used in all four events, another way to approach this problem would be to consider the likelihood of a member of the AR rifle family being used at these events amongst all makes and models of rifles and shotguns.  These numbers can be derived from Senator Feinstein’s Assault Weapons Ban legislation (ref).  Combining the 2258 cited “legitimate hunting and sporting rifles and shotguns” (by specific make and model) with the 118 proposed banned rifles and shotguns yields 2376 total available rifles and shotguns by make and model.  The legislation identifies 57 members of the AR rifle family by make and model (all AR rifles are proposed to be banned).  The AR rifles therefore constitute about 2.4% of all rifles and shotguns.  Again, assuming no bias in selection, the odds of a member of the AR rifle family being selected simply by chance in any of the individual events amongst all available types of rifles and shotguns becomes about 2.4 in 100 (0.024).  The odds of a member of the AR rifle family being selected in all four independent events simply by chance is less than 1 in 3 million (Note: this consideration includes all AR Rifles and excludes handguns as a potential weapon).

These results would support a conclusion that, in the latter half of 2012, the AR-15 was being intentionally selected for use in the premeditated, indiscriminate mass murder events identified here.


The purpose of this article was not to perform detailed statistical analyses of a broad array of events and weapons, but rather simplify the matter by selecting a specific type of event (as described above), examining the weapon used, and then using basic odds considerations in determining the likelihood of the weapon being selected simply by chance.  The odds that an AR-15 rifle would be selected simply by chance in all 4 of the identified events in the latter half of 2012 was found to be infinitesimally small under the assumptions and parameters used here.  And behavior of the shooters support an intentional selection.  The Aurora shooter purchased the firearm for the event; the Happy Valley shooter stole the weapon for the event; the Newtown shooter had access to multiple weapons but used the AR-15 as the primary (firing 151 of the total 152 bullets from that weapon – the last came from a handgun he used to kill himself); and the Webster shooter (who was prohibited from owning a firearm being a felon) obtained the weapon through a ‘straw purchase’.

If one wishes to strip away the definitions used here, the finding that an AR-15 (that constitutes but 1% of all firearms held by US civilians) was found in a majority of all of the ‘mass shooting’ events (5/9) considered here in the latter half of 2012 is striking.  But defining a specific type of event is felt to be important as an event could influence weapon selection.  The intent to kill one’s boss or spouse, as examples, would not require the use of a ‘military-style’ rifle like the AR-15.  However, the premeditated indiscriminate killing of multiple individuals would likely involve the selection of a weapon the shooter felt would best accomplish the task.  And the development/history/appearance (and thus perception) of the AR-15 separates it from most other handguns, rifles, and shotguns in that regard.

Although arguments have been made that there are other more powerful weapons available to US citizens than the AR-15, the power of a weapon would not seem to be the desired feature for the events considered here.  It would be the ability of the firearm to rapidly and accurately claim as many lives as possible.  Again, the history and appearance (and thus perception) of the AR-15 would make the weapon well-suited to the selection.

There is little doubt that the assailants in these events were disturbed and a proposed solution is to address mental illness rather than the weapon.  Lanza (the shooter in the Newtown incident) could be restricted under law from purchasing a firearm and placed into a database, but he took the weapons from his mother’s home after putting multiple bullets into her head (should the AWB legislation become law, it would leave 3 million of these weapons in civilian hands).  And the shooter in the Webster NY incident was already prohibited from purchasing a firearm (being a felon), but obtained the weapon through a straw purchase.  As long as the weapon remains available and is being actively sought for these types of events, it will find its way into the wrong hands.  And the NRA’s proposed tightening up the mental health system, or increasing federal and state resources in going after the less-than-law-abiding, is disingenuous as the organization supported legislation making it easier for the mentally-ill to regain their gun rights (ref) and Grover Norquist, whose stated purpose is to shrink government to the size he can drown in a bathtub, holds a board position (ref).

Although there has been much discussion of ‘assault weapons’ being used this past year in several mass shootings, it is felt that the considerations presented here fundamentally change the assault weapons debate.  It is not just that the AR-15 rifle was being used in these events, there is little if any doubt that it was being intentionally selected as a weapon of choice in premeditated indiscriminate mass murder events of the horrific nature we witnessed in the latter half of 2012.  Keeping this weapon unregulated and increasing public availability could only increase the opportunity for its use in future mass shootings of the nature we witnessed in 2012.

This places lawmakers who oppose the AWB into a troublesome position.  Are they willing to leave a weapon unregulated knowing that it is being intentionally selected for indiscriminate mass killings in the civilian population (what its look-alike version was designed to do in battle)?  Or if they remain opposed to a ban, would they also be opposed to limiting the magazine capacity of a weapon being sought for such horrific events?  (Maddow makes the point that Lanza had to reload the AR-15 only four times over a space of 5 minutes in Sandy Hook Elementary rather than 14 times had the magazines held only 10 bullets).  Or are they willing to keep their position that regulating this product is an infringement on the rights of, or an imposition to, ‘law abiding’ citizens.  It is important to note that Supreme Court justices in both the Heller and McDonald rulings made clear that the Second Amendment did not confer ‘a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose’ and that a wide range of gun control laws remain ‘presumptively lawful’ including prohibiting ‘dangerous and unusual weapons’.  A legal summary of both cases is provided here.

But for lawmakers to not address this matter at all, would speak to a dereliction of duty.