The Patterns of Mass Killing

If you were only listening to the political debate following the mass murder in Newtown, Connecticut, you might think that most such mass murders were perpetrated using “assault weapons” and that the murderers generally attacked strangers. That, apparently, is not the case:

The basic pattern found by the New Jersey DHS fusion center, and obtained by Public Intelligence (.PDF), is one of a killer who lashes out at his co-workers. Thirteen out of the 29 observed cases “occurred at the workplace and were conducted by either a former employee or relative of an employee,” the November report finds. His “weapon of choice” is a semiautomatic handgun, rather than the rifles that garnered so much attention after Newtown. The infamous Columbine school slaying of 1999 is the only case in which killers worked in teams: they’re almost always solo acts — and one-off affairs. In every single one of them, the killer was male, between the age of 17 and 49.

They also don’t have military training. Veterans are justifiably angered by the Hollywood-driven meme of the unhinged vet who takes out his battlefield stress on his fellow Americans. (Thanks, Rambo.) In only four of the 29 cases did the shooter have any affiliation with the U.S. military, either active or prior at the time of the slaying, and the fusion center doesn’t mention any wartime experience of the killers. Yet the Army still feels the need to email reporters after each shooting to explain that the killer never served.

It’s harder to construct patterns around shooter motives, the report notes, since in most cases the killer takes his own life or gets killed by law enforcement before publicizing his reasons for violence. But DHS warns that “indicators of potential violence” include a worker’s abrupt and persistent absenteeism; “escalation of domestic problems into the workplace; talk of severe financial problems”; a notable decline in “attention to appearance and hygiene”; unsolicited empathy with the perpetrators of mass violence; and vocalized musings about suicide. The fusion center doesn’t offer more granular data.

The weapons in question, semiautomatic handguns, are also the weapon of choice in gang slayings so you might think that a coherent policy would target those weapons. The emphasis on “assault weapons” suggests otherwise.

Something we should keep in mind: even in the United States the number of these mass killings is actually quite small. It’s difficult to come up with robust findings from such small datasets. It is, however, easy to make political hay over tragedies so who cares whether the bills that will eventually be based will actually accomplish anything?