Suspects in mass killings are almost always men, making the rampage in San Bernardino — in which a husband and wife allegedly burst into a holiday party and killed 14 people — a statistical oddity.
Syed Rizwan Farook, 28, and wife Tashfeen Malik, 27, unleashed a hail of bullets on a conference room at the Inland Regional Center, a state-run facility for people with developmental disabilities, at about 11 a.m., authorities said. They were killed about four hours later in a shootout with police.
It's rare for a mass shooter to be female: Less than three percent of killers in public mass shootings over the last three decades have been women, according to a database compiled by Mother Jones.
Even in the broader category of mass killings, which includes other methods of execution, such as arson, only six percent of perpetrators are female, according to a database compiled by USA TODAY.
Jodi Upton, who runs the data journalism team at USA TODAY, told NBC News that about 70 percent of mass killings are done by firearms — but not usually the ones committed by women.
"There's very few women who commit mass killings. But of those who do, there's a slight tendency to prefer drownings or strangulation or arson," she said in July.
Mother Jones used a strict set of criteria for a mass shooting for their database. They looked at incidents in which at least four people, not including the shooter, were killed, that took place in a public place (not a private residence), usually in a single location.
Out of 73 incidents that met that criteria, just two public mass shootings since 1982 before the San Bernardino attack involved a female killer.
The Alturas tribal shooting
On Feb. 20, 2014, Cherie Lash Rhoades, 44, former chairwoman of the Cedarville Rancheria tribe, opened fire at the Cedarville Rancheria Tribal Office and Community Center in Alturas, California. Among those killed were her brother, her niece, and her nephew. When she ran out of ammunition, she grabbed a butcher knife and stabbed another person. All told, she killed four people and wounded two. Authorities said the meeting at tribal headquarters was about evicting Rhoades and her son from tribal land.
The Goleta postal shooting
On Jan. 30, 2006, former postal worker Jennifer San Marco, 44, fatally shot a former neighbor in Goleta, California, then drove to the mail processing plant where she used to work. She opened fire inside, killing six employees before killing herself. The U.S. Postal Service said that San Marco worked for the Postal Service for six years, but was given early retirement in June 2003 because of psychological problems.
There's also a handful of female shooters who don't meet the criteria for mass shooters, but whose rampages were high-profile nonetheless:
- On Jan. 29, 1979, Brenda Spencer, 16, fired 36 shots from a .22-caliber semiautomatic rifle on a San Diego elementary school. Two adults were killed and eight children were wounded.
- On Oct. 31, 1985, Sylvia Seegrist opened fire on a suburban Philadelphia mall, killing two people and wounding eight others.
- On May 20, 1988, Laurie Dann, a 30-year-old with a history of mental illness, delivered arsenic-laced desserts and juice boxes to families for whom she had babysat. Later in the day, she drove to an elementary school in Winnetka, Illinois, with three guns and killed one student and injured five others.
- On Feb. 12, 2010, Amy Bishop, a biology professor, shot up a University of Alabama-Huntsville faculty meeting, killing three colleagues and wounding three others.