Why older mass shooters like the California gunmen are so rare

The gunmen in both of the recent shootings in Monterey Park and Half Moon Bay, California, had an unusual profile compared to most perpetrators of violent crime: They were both senior citizens.

The Monterey Park gunman, who killed 11 and injured nine before fatally shooting himself, was 72. The Half Moon Bay gunman, who killed seven people before he was arrested in what police have characterized as an act of workplace violence, is 66.

Mass shooters of that age are rare, especially those with no prior criminal record, as was the case with the Half Moon Bay gunman. (The Monterey Park gunman had one arrest in 1990 for illegal possession of a firearm.) According to data from the National Institute of Justice, mass shooters between 1966 and 2021 were on average 34 years old, and those over the age of 60 accounted for a little over 3 percent of all mass shootings, which are defined as shootings in which four or more people are killed.

The notion that people “age out of crime” is one of the most well-documented phenomena in the field of criminology. The California shootings should be seen as exceptions to that principle, not as nullifying examples, according to Ashley Nellis, co-director of research for the Sentencing Project, which advocates for criminal justice reform.