A new government report says half of the mass attacks in the United States over the past few years started as personal, family, or workplace disputes.
The attackers, the report found, were mostly men.
The attackers often have a history of mental health issues, money problems or domestic violence.
Their weapons of choice: guns.
The report was released Wednesday by the U.S. Secret Service's National Threat Assessment Center.
The 70-page report studied 173 mass attacks carried out over a five-year period, from January 2016 to December 2020.
The mass attacks happened in places such as businesses, schools and religious centers.
The attacks killed a total of 513 people and injured 1,234.
"It's just happening way too often," said Lina Alathari, the center's director.
Alathari said that while the center did not study the two most recent shootings in California, there are themes seen "over and over again" when studying mass attacks.
Officials said the suspects in both recent California shootings were older men.
They both used semi-automatic guns.
The report is the latest in a series undertaken by the center to examine mass attacks.
Earlier reports examined the years of 2017, 2018 and 2019.
But the new report noted that it examines several years of data, which offers more "in-depth analysis of the thinking and behavior of mass attackers."
The center defines a mass attack as one in which three or more people — not including the attacker — were harmed.
The report noted that nearly two-thirds of attackers showed behaviors or communications "that were so concerning, they should have been met with an immediate response."
It said these concerns were often shared with law enforcement, employers, school workers or parents.
But in 20 percent of the cases, the concerning behavior was not communicated to anyone who could do something about it.
Ninety-six percent of the attackers were men.
The attackers ranged in age from 14 to 87.
The report called for greater attention toward violence at home.
It noted that half of the attackers had a history of domestic violence or hatred toward women.
About half the attacks in the study involved workplace violence related to co-workers, customers or businesses.
The report said workplaces should establish "behavioral threat assessment programs" to prevent possible violence.
And it said businesses should work with law enforcement to deal with "incidents involving a concern for violence."
The report also found that firearms were used in 73 percent of incidents.
Mass shootings happen often in the United States.
But American lawmakers remain divided on how to deal with gun violence.
Democrats are calling for more gun control measures, while Republicans' calls center on mental health and increased security.
Last June, the U.S. Supreme Court expanded the right to carry guns outside the home.
The court struck down a state law in New York that required people to show a specific need to carry a firearm in public.
I'm Ashley Thompson.