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, law enforcement officials said yesterday.
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.
A total of 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 the police arrived. The gunman acted alone in all but two of the cases.
Not all of 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 the police.