FBI: Mass shootings are on the increase

The number of shootings in which a gunman wounds or kills multiple people has increased dramatically in recent years, with the majority of attacks in the last decade occurring at a business or a school, according to an FBI report released on Wednesday.

The study focused on 160 "active shooter incidents" between 2000 and 2013. Those are typically defined as cases in which a gunman in an attack shoots or attempts to shoot multiple people in a populated area.

The goal of the report, which excluded shootings that are gang- and drug-related, was to identify common themes and to help local law enforcement prepare for or respond to similar killings in the future, officials said.

"These incidents, the large majority of them, are over in minutes. So it's going to have to be teaching and training the best tactics, techniques and procedures to our state and local partners," said James F. Yacone, an FBI assistant director who oversees crisis response and was involved in the report.

According to the report, an average of six shootings occurred in the first seven years that were studied. That average rose to more than 16 shootings per year in the past seven years of the study.

That period included the 2012 shootings at a movie theater in Aurora, Colorado, and at Sandy Hook Elementary School in Newtown, Connecticut, as well as last year's massacre at the Washington Navy Yard in which a gunman killed 12 people before dying in a police shootout.

The majority of the shootings occurred either at a business or a school, university or other education facility, according to the study, conducted in conjunction with Texas State University.

Other shootings have occurred in open spaces, on military properties, houses of worship and healthcare facilities.

More than 1,000 people were either killed or wounded in the shootings. In about one-quarter of the cases, the shooter committed suicide before police arrived. The gunman acted alone in all but two of the cases.

Not all the cases studied involved deaths or even injuries. In one 2006 case in Joplin, Missouri, a 13-year-old boy brought a rifle and handgun into a middle school, but his rifle jammed after he fired one shot.

The principal then escorted the boy out of school and turned him over to police.

Law enforcement officials who specialize in behavioral analysis say the motives of gunmen vary, but many have a real, or perceived, personally held grievance that they feel mandates an act of violence.

Though it's hard to say why the number of shootings has increased, officials say they believe many shooters are inspired by past killings and the resulting notoriety.

"The copycat phenomenon is real," said Andre Simons of the FBI's Behavioral Analysis Unit.

"As more and more notable and tragic events occur, we think we're seeing more compromised, marginalized individuals who are seeking inspiration from those past attacks."