June 21 (UPI) -- An FBI examination of shooting attacks over a 13-year period in the United States has concluded that most shooters obtain their firearms legally, and the majority had not been diagnosed with mental illness.
The 29-page FBI report sheds light on "active shooters" and their behaviors before the attacks, and dispels somewhat the notion that most mass shooters are mentally ill and obtain their weapons unlawfully.
The study covered 63 incidents that occurred between 2000 and 2013 and found 75 percent were carried out by perpetrators who legally owned their guns. Of those, 40 percent bought their guns specifically for the attack and 35 percent owned the weapons before the assault.
Further, the FBI found that only a quarter of shooters in the cases had been diagnosed with mental illness -- but all except three had exhibited behavior that concerned others. In more than half of the cases, law enforcement had not been notified of those concerns before the attacks.
"In light of the very high lifetime prevalence of the symptoms of mental illness among the U.S. population, formally diagnosed mental illness is not a very specific predictor of violence of any type, let alone targeted violence," the FBI report said. "Careful consideration should be given to social and contextual factors that might interact with any mental health issue before concluding that an active shooting was 'caused' by mental illness."
The analysis also found the shooters usually planned their attacks well in advance, with 77 percent spending a week or more laying out the plot.
The report noted the attackers were almost always men or boys -- only four of the 63 cases involved female perpetrators -- and the attacks were largely motivated by grievances in the shooters' personal lives, and targeted specific victims.
Other demographics found the average age of the shooters was 37; the youngest was 12 and the oldest 88. Sixty-three percent were white, 16 percent were black, 10 percent were Asian, 6 percent were Hispanic, 3 percent were from the Middle East and 2 percent were Native American.
The report specified 30 active shootings in the United States in 2017, the largest number recorded by the FBI for a one-year period.