Since Aurora theater shooting: 387 dead in mass killings

Meghan Hoyer | USA TODAY

In the three years since James Holmes shot dozens of moviegoers in Aurora, Colo., 78 additional mass killings have occurred, claiming the lives of nearly 400 additional victims.

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That includes major public tragedies such as the slayings of 26 people, mostly children, at a school in Newtown, Conn., the recent shootings of nine people in a Charleston, S.C. church, and the Boston Marathon bombings. It also includes less-publicized tragedies, such as a deliberately set fire that killed six family members in McKeesport, Pa., in 2014 and the shootings of four young men on a downtown San Francisco street in January.

USA TODAY has kept a tally of mass killings -- defined as the slayings of four or more people, not including the suspect -- dating back to 2006. The data show that mass killings occur roughly every two weeks, a figure that has remained steady for the past decade.

There have been 15 mass killings so far this year, claiming 74 lives. Two have occurred in the past two days: the shootings of two adults and two teenagers in Holly Hill, S.C. Wednesday and four Marines gunned down at a military recruitment center in Chattanooga, Tenn., today. Roughly 80% of the mass killings in the past three years have involved guns.

But criminologist James Alan Fox of Northeastern University said gun control isn't necessarily the answer. USA TODAY's data shows most guns used in mass killings are handguns, and are often legally obtained.

"When we have these incidents, they tend to motivate people to want to do something about it, and that's a good thing," said Fox, the author of Extreme Killing. "But the kind of crime that's probably most difficult to prevent are these extreme, but rare cases."

Fox said most mass killings aren't like Aurora – entirely random acts of violence. Most have specific targets or specific motives, such as killing family members or making a political point. And when mass killers are thwarted by gun checks or are treated for mental health issues, most are motivated enough to find ways around the system.

"I know people want to round up all the guns, and round up all the people considered dangerous," Fox said. "That's easier said then done."