Many, though not all, of the perpetrators have experienced childhood traumas such as physical or emotional abuse, and unstable families, with violent, absent or alcoholic parents or siblings, for example. And most have experienced significant losses.

For example, the defendant in the case of the Parkland, Fla., shooting last year had lost his adopted mother to complications from the flu just a couple of months before the school attack. His adopted father had died when he was a little boy.

Read the full article here.