“Mass shootings are domestic violence events much more commonly than the public believes,” Garen Wintemute, who heads the Violence Prevention Research Program at the University of California, Davis, told BuzzFeed News by email.

What’s more, women who’ve previously been assaulted by their partners are at high risk of being murdered if there are firearms in the house. Yet states differ on restrictions on gun ownership for domestic abusers, and researchers still don’t know whether the perpetrators of domestic violence present a high risk for gun homicide more generally.

The mass shootings that attract most attention are those that happen in public places, ending the lives of apparently random victims. But a 2015 report by the Congressional Research Service, covering incidents from 1990 to 2013 in which four or more people were killed, found that “familicides,” involving the murders of former intimate partners or family members, were the most frequent, and accounted for the largest number of deaths.