Some of it appears to lie in their (“our”) biological vulnerability. … about 30% of males (versus 9% of females) have a form of the MAOA gene that reduces the levels of an important neurotransmitter, and this in turn impairs their ability to deal effectively and prosocially with stressful situations …

But [genetics] is only a part, perhaps a small part, of the larger story. Males are also especially immersed in a culture that glorifies and justifies violence, and particularly male violence. …

These cultural messages and themes poison male consciousness. To put it bluntly, although the mentally ill on average are no more violent than the sane, even “crazy people” act within a cultural framework. They respond to cultural scripts that tell them “if this, then that.” For example, no account of the massacre of nine African Americans in a Charleston, South Carolina, church in June of 2015 is sensible without the recognition that there is a long tradition of racism as a rationale for killing black people in America…

…

All of these factors are compounded when the issue is young males. In recent decades, neuroscience researchers have demonstrated that human brains do not mature fully until people reach their mid or even late 20s, for the most part. These immature brains are particularly prone to make mistakes in interpreting the meaning of emotions in others, of judgment, and in assessing the risks and benefits of action. …

What is more, when young males have had an accumulation of adverse childhood experiences, the odds that they will have problems with both emotional regulation and executive function increase….

Finally, of course, there is the matter of arming troubled young male with lethal weapons. It is the access to guns that makes young male people so dangerous, especially when they are troubled, angry, or somehow “crazy.” …

Despite growing gender equality with respect to access to guns culturally and physically, it remains true that males are more gun-identified than females. And it is guns that make American violent behavior so lethal. Guns make suicide attempts particularly deadly (85% lethal vs. less than 10% for pills). It is guns in the hands of males that make domestic disputes—mostly violence against women—so dangerous. It is guns that make cop–civilian confrontations so deadly (most of which involve males on both sides). It is guns that make racist ideologies in the heads of troubled young males lead to nine dead bodies in a church in South Carolina, because “guns don’t kill people; people with guns kill people.” Or more accurately, “male people with guns.”

From the commentary, “Mass Murder: A Perspective on Young Male Killers“, Violence and Gender. 2:3, September, 2015.