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The two men who just days apart in California are the latest perpetrators in America's long history of mass gun violence. But something about these public shootings, and the men held responsible, stands out.

The . Yet the man who is alleged to have on Jan. 21, 2023, before turning the gun on himself —t³ó±ð , our records show. Meanwhile, the gunman who two days later was also —66, the third-oldest in history.

are who of 191 mass shooters using public data. The shooters in our records date back to 1966 and are coded on nearly 200 different variables, including age at the time of attack. Our research shows that mass shootings— as events in which four or more people are killed in a public place with no underlying criminal activity—have become more frequent, and deadly, over time.

Prior to the January 2023 Californian shootings, mass shooters were also . From 1980 to 1989, the median age of mass shooters was 39. Over the next two decades, it was 33. And from 2010 to 2019, it was 29.

Since 2020, the median age of mass shooters has come down to just 22 years old—mostly young men and boys who were born into or came of age in an and carried out their attacks .

Older mass shooter behind deadliest assault

Ages vary by shooting location, . Though mass shooters at offices, warehouses and houses of worship skew older, shooters at K-12 schools, colleges and universities tend to be younger—in large part because many school shooters tend to be current or former students.

Prior to the tragic incidents in Monterey Park and Half Moon Bay, just six mass shooters in our study were over the age of 60. The oldest was a at an auto parts store in Kentucky in 1981. The list also includes the perpetrator of the deadliest mass shooting in U.S. history—a 64-year-old who in Las Vegas.

The others were a 66-year-old who was supposed to turn himself in to serve a prison sentence but instead where he used to work in Illinois in 2001; a 64-year-old who in rural New York in 2013; a 62-year-old who in 1997 in New Hampshire, including two state troopers and a judge; and a 60-year-old in Palm Bay, Florida, in 1987.

Nearly all of the over-60s perpetrators of mass shootings prior to the January 2023 Californian incidents were white men—just one was a nonwhite male. This differs in the Monterey Park and Half Moon Bay incidents, both of which are thought to have been carried out by Asian Americans.

Less likely to leak details of attack

Mass shooters over 60 also tend to have prior criminal records and to target their place of employment, or retail and outdoor locations in communities they knew well.

What separates the older mass shooters from their younger counterparts is that mass shooters in their 20s and 30s typically study previous mass shooters for inspiration and validation. Younger shooters also tend to in advance. This practice, known as leakage, is often seen as a final cry for help. Younger shooters also tend to leave behind manifestos to communicate their anger and grievances to the world, the data shows. suggest they are seeking fame and notoriety for their actions.

None of the shooters aged 60 and above in our database did that—although investigations are ongoing in the back-to-back California cases. Instead, they tend to have experienced a recent stressor, such as a family conflict or debt. They are more likely to be motivated by legal, financial and interpersonal conflicts, not hate or fame-seeking like many of their younger counterparts.

But all perpetrators of mass shootings, young and old, have some things in common. Their mass shooting is intended to be their final act. Whether they die by suicide—as is , are killed on scene, or , mass shootings are a final act of hopelessness and anger.

They also have access to the firearms they need to commit these devastating crimes.

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