Mass shootings are hard to define and definitions vary. After the Newtown tragedy, Congress defined a “mass killing” as “3 or more killings in a single incident.” The FBI defines “mass murder” as “a multiple homicide incident in which four or more victims are murdered, within one event, and in one or more locations in close geographical proximity.” And the FBI’s definition of “mass shooting” is “a multiple homicide incident in which four or more victims are murdered with firearms, within one event, and in one or more locations in close proximity.” Finally, a “public mass shooting” is defined as “a multiple homicide incident in which four or more victims are murdered with firearms, within one event, in at least one or more public locations, such as, a workplace, school, restaurant, house of worship, neighborhood, or other public setting.” Regardless of the definition used, the United States (US) has, by far, more mass shootings than anywhere else in world. And mass shootings in the US are on the rise.

Mental illness is over- and mis-represented as the cause of gun violence, especially mass shootings. Analyses of public mass shootings have shown that the minority of shooters - between 15 and 22% - have serious mental illness.

It is important to know that 54% of mass shootings between 2009-2016 were committed by intimate partners or family of the victims. Most “mass shooting” events occur in private spaces, usually related to domestic violence (i.e., they are not “public mass shootings”). They don’t often makes the news.

In a sample of 160 active shooting incidents identified by the FBI from 2000 to 2013, only one was stopped by armed civilian. In comparison, two were stopped by off-duty police officers, four by armed guards, and twenty-one by unarmed civilians. 

The original 1993 Brady Handgun Violence Prevention Act (“Brady Bill”) had an assault weapons ban (this expired in 2004). In one analysis there were 2.05 public mass shootings per year from 1973 to 1994. During the ban years there were 1.6 per year. Public mass shootings increased to 4.18 per year after the ban expired.

Gun shot injuries are increasingly likely to lead to death, likely due to the proliferation of assault weapons and high capacity magazines since the assault weapons ban expired. When a mass shooting involves an assault weapon or a high capacity magazine, more people are shot and/or killed compared to other mass shootings.

Take a look at this report from the Congressional Research Service for more information.

Also, check out the report, “Mass Violence in America: Causes, Impacts and Solutions,” from the Medical Director Institute of the National Council for Behavioral Health.