Thoughts & Prayers

According to Mother Jones' data, there were 150 mass shootings with a total of 1153 fatalities between 1982 and 2024.

Under one of the most conservative definitions of “mass shootings,” in which a gunman slaughters four or more strangers in a public place, the number of these crimes has indeed been climbing in the last few years — and they have higher death tolls, as well.

Mass shootings account for just a fraction of the daily toll of firearm deaths in the U.S., where about 124 people die every day in other acts of gun violence.

Here is a description of the criteria Mother Jones uses to define a mass shooting:

• The perpetrator took the lives of at least four people. A 2008 FBI report identifies an individual as a mass murderer—versus a spree killer or a serial killer—if he kills four or more people in a single incident (not including himself), typically in a single location. (*In 2013, the US government’s fatality baseline was revised down to three; our database reflects this change beginning from Jan. 2013, as detailed above.)
• The killings were carried out by a lone shooter. (Except in the case of the Columbine massacre and the Westside Middle School killings, which involved two shooters.)
• The shootings occurred in a public place. (Except in the case of a party on private property in Crandon, Wisconsin, and another in Seattle, where crowds of strangers had gathered, essentially constituting a public crowd.) Crimes primarily related to gang activity or armed robbery are not included, nor are mass killings that took place in private homes (often stemming from domestic violence).
• Perpetrators who died or were wounded during the attack are not included in the victim tallies.
• We included a handful of cases also known as “spree killings“—cases in which the killings occurred in more than one location, but still over a short period of time, that otherwise fit the above criteria.

There is no national, legal definition of a “mass shooting.” Several organizations track mass shootings, but use different yardsticks: Some count only incidents in which three or more people are killed; others measure incidents with at least four people killed or injured.

Mass shootings are increasing

If it feels like mass shootings have become more frequent, that intuition is correct, according to a narrow definition of mass shootings used by the Congressional Research Service and data about such incidents collected by The Violence Project and Mother Jones.

Killer obtained their weapons legally?

In the aftermath of a mass shooting, a recurring question arises: How did the shooter get their gun?

In the majority of cases, the perpetrator legally bought the firearms in question. Of the 114 mass shootings committed in the U.S. since 1982, 85 (or 74%) involved firearms obtained by legal means.

Where did the rest of the guns come from?

Seventeen of the guns used in mass shootings in the last 36 years — roughly 15% — were obtained in other ways:

• In eight cases shooters took their guns from family members
• In four cases they were purchased illegally
• In three cases they were stolen
• In one case the shooter illegally kept his gun after loosing his state firearms license, which required him to surrender his firearm
• And in one case the shooter illegally built their own firearms

Ages of Mass Shooters

Mass shooters skew young. Grouping mass shootings by the age of the perpetrator show a cluster around early twenties and again towards mid-to-late forties.

Mass shootings by location and legal status

The majority of mass shootings relied on weapons obtained legally. They occurred in places familiar to every American: places of worship, schools, workplaces, etc.

Weapons of war

Grouping the weapons used in mass shootings into categories highlights a grisly trend - the growing popularity of semiautomatic rifles with high-capacity magazines. Such weapons, designed for the battlefield, allow an unskilled marksman to fire dozens of shots in seconds with deadly ease.

Just about any weapon can use a high-capacity magazine, with the exception of a revolver and a cannon and probably a few others I'm forgetting. These magazines allow a firearm to carry more ammunition, allowing a shooter to fire more rounds before having to reload the weapon.

Any weapon with a high capacity magazine made a significant difference in the number of casualties, expect when compared an assault weapon.

Below is a comparison table of all the weapons used. I used what's called a Dunn's Test to compare them. Any p-value of 0.05 or below is considered statistically significant and has been highlighted. Both an assault weapon and high-capacity magazines resulted in a similar amount of carnage.

It's challenging to visualize the differences between the different types of weapons (the groups) because the data is not normally distributed, making it hard to clearly spot patterns. Many statistical tools depend on the normal distribution (i.e., a bell curve) of data in order to work. Dunn's Test address this by ranking the data. In this case we would take the shooting with the least amount of casualties and rank it first. Then the next largest number of casualties would be ranked second, then the next, and so forth. We continue this process until all the data has been ranked. Dunn's test then makes comparisons across all the groups to see where there is a statistical difference. This is what is plotted above.

Illustration

The image caption for this article is the aptly titled "Thoughts & Prayers" by Adam Williams. I encourage you to check out the powerful essay he wrote about the artwork as a father.