James Densley

The two men who shot dead 18 people in separate incidents j\ust days apart in California are the latest perpetrators in Americas long history of mass gun violence. But something about these public shootings, and the men held responsible, stands out.

The median age of mass shooters in the United States is 32. Yet the man who is alleged to have shot dead 11 people in Monterey Park on Jan. 21, 2023, before turning the gun on himself was 72 years old the oldest mass shooter in modern American history, our records show. Meanwhile, the gunman who took the lives of seven more in Half Moon Bay was also older than most 66, the third-oldest in history.

We are criminologists who built a database 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 defined here 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.