And as for 2013....
"We've Had So Many Mass Shootings In The U.S., We've Had To Redefine The Term"......
http://www.huffingtonpost.com/2013/09/17/mass-shootings-us_n_3935978.html
Snippet :
"The growing number of mass killings over the past five years left the country in search of a term that would distinguish mass murder by gun from those using other weapons. Mass shooting has gained favor as the obvious choice. Though the FBI doesn't specifically define mass shooting, it does define mass murder, calling it a single incident in which a perpetrator kills four or more people, not including himself or herself.
The FBI defined mass murder to distinguish it from serial murder. That definition provides the basis for the unofficial definition of mass shooting that has gained use in recent years. Mother Jones explained the definition in an extensive "Guide to Mass Shootings in America," writing that mass shootings typically involve a single episode in a single location, usually a public place. The Mother Jones definition of mass shooting matches the FBI definition of mass murder in that it includes single incidents that kill at least four victims.
Over on Reddit, the Guns Are Cool community has compiled a list of every mass shooting in the United States this year. The moderators of the subreddit, which doesn't actually appear to be of the belief that guns are cool, use an expanded definition of mass shooting, listing every event in which "four or more people [including the shooter] are shot in a spree." Under the Reddit definition, a shooting spree that wounds at least four people, but doesn't kill them, is still a mass shooting.
Including Monday's mass shooting, the Reddit list for 2013 is nearing 250 incidents. That's an average of one mass shooting almost every day....."