There obviously has to be some explanation, but as of now the most likely theories don't seem to be getting anywhere in explaining why Jason Dalton suddenly and randomly murdered six people in Kalamazoo last Saturday. In addition to having neither a criminal record nor a history of mental health problems, early speculation of financial and marital problems appear to have been baseless.
All we've got is his wife having told him a couple days before the shooting that he seemed uncharacteristically down and depressed. It appears she didn't know why. As of now, neither do any of us: