Older suspects in California shootings defy typical mass shooter profile

Given the rarity of the subjects, researchers know relatively little about the older perpetrators of mass public shootings

As California, and the United States, reel from two devastating mass shootings in three days that have left 18 people dead and many more injured, detectives are combing through the crime scenes in Monterey Park and Half Moon Bay in search of motives.

One aspect they will have to grapple with that makes the California tragedies stand out from the grim pack of American gun massacres is the older age of the shooters. In both cases the alleged killers were in their 60s and 70s, placing them in a very rare group.