Mass shootings in America: Anatomy of a hyped statistic

These examples show how compiling data on shooters can be subjective. The agreed-upon definition of an “active shooter” – the phrase is codified in U.S. law – is simply “an individual actively engaged in killing or attempting to kill people in a confined and populated area.” The most prevalent definition of a “mass murder” in this context is four or more victims. This means that Brenda Spencer, the 16-year-old girl who fired on San Diego’s Cleveland Elementary School from her home across the street in 1979, isn’t always listed as a mass shooter because she only killed two people — though she wanted to kill more.

But the death toll is not irrelevant to shooters’ motives. Criminologists who’ve studied them believe that body counts play a role in their calculations. So does media coverage. In the 1980s, there were 30 known instances of mass shooters. Those included the appalling 1984 shooting at a McDonald’s restaurant in the California border town of San Ysidro and the 1986 massacre of U.S. Postal Service workers in Edmonds, Okla., by a postal employee and former Marine Corps marksman named Patrick Sherrill. In killing 14 and wounding six. Sherrill started a spate of such shootings by mail service employees, giving rise to the self-fulfilling description “going postal.”