Generally speaking, says Lin Huff-Corzine of the University of Central Florida, women do not kill as often as men. She and other researchers have cooperated on an upcoming article for the quarterly journal , based on data from the FBI. Between 2001 and 2010, less than 8 percent of mass murder offenders in the U.S. were women, she says, adding that some of the women included in the statistics assisted in a crime but did not pull a trigger.

In part, Huff-Corzine says, “this may be explained by women’s weapons of choice even when they do want to do serious bodily harm to someone. Specifically, men are more comfortable than women when using guns, whereas women are more likely to choose knives. Guns are simply more effective than knives when killing another person. This is especially the case when three or more people are murdered.”

And, Huff-Corzine says, “women are comfortable with being less lethal.”