Amanda Taub writes: One of the first things we learned about Omar Mateen, the gunman in the nightclub massacre in Orlando, Fla., was that his ex-wife said he had beaten her severely until she left him in 2009.

If it sounds familiar that a gunman in a mass shooting would have a history of domestic violence, it should.

In February, Cedric Ford shot 17 people at his Kansas workplace, killing three, only 90 minutes after being served with a restraining order sought by his ex-girlfriend, who said he had abused her. And Man Haron Monis, who holed up with hostages for 17 hours in a cafe in Sydney, Australia, in 2014, an episode that left two people dead and four wounded, had terrorized his ex-wife. He had threatened to harm her if she left him, and was eventually charged with organizing her murder.

When Everytown for Gun Safety, a gun control group, analyzed F.B.I. data on mass shootings from 2009 to 2015, it found that 57 percent of the cases included a spouse, former spouse or other family member among the victims — and that 16 percent of the attackers had previously been charged with domestic violence.

Social scientists have not settled on an explanation for this correlation, but their research reveals striking parallels between the factors that drive the two phenomena.

There are, of course, a tangle of factors behind every murder, especially terrorism inspired by foreign groups. But research on domestic violence hints at a question that often arises from seemingly inexplicable events like Mr. Mateen’s massacre of 49 people at an Orlando nightclub — what drives individuals to commit such mass attacks? — and sheds light on the psychology of violence. [Continue reading…]