As convenient as it would be, there is no one-size-fits-all profile of who carries out mass shootings in the United States.

About the only thing almost all of them have in common is that they are men.

But those men come from varying backgrounds, with different mental health diagnoses and criminal histories. Examining past New York Times coverage of mass shootings reveals some shared tendencies of the gunmen, including the fact that they are most commonly white, but such traits also describe thousands of law-abiding Americans who don’t become murderous.

The United States’ high number of mass shootings is best explained by the availability of guns, as fully explained here. But here is some of what we do know about the motivations and histories of the gunmen.

Mental illness

Experts say the people willing to kill strangers don’t all have a certain mental illness, and in many cases never sought professional help. They are often paranoid, resentful or narcissistic, but not always to the extent that they had been found to have a disorder.