Mental health factor in trying to reduce mass killings.

• Position: NEWS

Byline: Lee Hammel

At least 56 mass shootings have occurred in the United States in the past four years and a national gun control group found no evidence that even one of the shooters was prohibited under federal law from possessing a firearm for mental health reasons.

Mayors Against Illegal Guns said Friday there was a mass shooting - defined by the FBI as an incident where at least four people are murdered by a firearm - more than once a month over a four-year study period from January 2009 through last month.

"We did not find evidence that any of the shooters were prohibited from possessing guns by federal law because they had been adjudicated mentally ill or involuntarily committed for treatment," said the 800-member mayors' group. Thomas M. Menino of Boston and New York's Michael R. Bloomberg are chairmen of the group.

But, "in 4 of the 56 incidents (7 percent), we found evidence that concerns about the mental health of the shooter had been brought to the attention of a medical practitioner, school official or legal authority prior to the shooting," the organization reported. "In another 4 incidents (7 percent), the shooter's mental health problems were known to friends or family but were not reported or known more widely until after the shooting."

Though still a small percentage of the shootings included in the study, the findings suggest that mental health issues may in some cases be flying under the radar when it comes to screening those seeking to legally acquire a firearm.

Mental health reasons are part of the backbone of a federal system, the National Instant Criminal Background Check System or NICS, designed to keep weapons out of the hands of undesirables and to reduce mass killings.

The mayors' group had sufficient evidence to judge whether the shooter was prohibited under federal law from having a gun in 42 of the 56 shootings.

It found that 15 of the 42 were prohibited because they were felons or certain domestic abusers - but not adjudicated mentally ill - and 27 (64 percent) were not prohibited.

It found that assault weapons or high capacity magazines were used in 23 percent of the incidents. When they were used, more than twice the number of people were shot (15 instead of 7) and 57 percent more were killed (8 instead of 5).

Mass shootings - from the 20 first-graders and six adults killed in a Connecticut elementary school in December to the congresswoman who survived an attack two years ago in Tucson, Ariz., that killed a federal judge and five others - has prompted renewed gun-control efforts at...