Some do it to perversely change the world. Others are driven to violence by mental illness, pandemic isolation, or social media.
Killers like 21-year-old Robert "Bobby" Crimo III, accused in Monday's Independence Day parade attack in Highland Park, Illinois, are younger than before. Researchers are trying to understand why to stop the next one.
Trending younger. Katherine Schweit, a former FBI agent who led the bureau's Active Shooter Program until 2017, said the "why" will take more research.
Many of them are suffering from pandemic stress and being indoctrinated online. Looking for fame."
In the past, most mass shooters in the U.S. were disgruntled employees who killed coworkers or family members out of anger or stress.
New research shows that one of the biggest threats comes from angry young men who live with their families and spend hours online with others who share their grievances and admiration for bloodshed.
Young men in America are prone to violence because they're trying to fit in with their peers and find their place in the world. While becoming independent of their parents and the social safety net, they often face rejection and alienation.
Internet and social media platforms have amplified these pressures over the past decade, researchers and law enforcement officials told USA TODAY.