Well, this would fit the evidence regarding the link between domestic violence and mass shootings.
More than two-thirds of mass shootings are domestic violence incidents or are perpetrated by shooters with a history of domestic violence, according to one of the first peer-reviewed research papers exploring the links between domestic violence (DV) and mass shootings. The paper also finds that...
efsgv.org
ETA: A link which is far more evidence-based than the supposed link to mental illness, I might add. It's easy to think, well I could never do something the cruel and horrible unless I "lost my mind," therefore people who do this must be mentally ill. But in actuality, some people are just violent, and usually there is other evidence of violence somewhere in their lives, whether anyone has ever reported it or not.
Findings from the Columbia database help dispel the myth that having a severe psychiatric illness is predictive of who will perpetrate mass murder.
www.columbiapsychiatry.org