Story highlights Sociologist Michael Kimmel wonders why young men are targeting strangers for revenge

Other factors vary, he says, but shooters are almost always male and very often white

Kimmel contends that a culture of violence linked with masculinity fuels the events

For the past few days, Americans have been weeping together and wringing our hands once again at the senseless tragedy of a mass murder inside a school. The horrific scene in Newtown, Connecticut , is now seared permanently in our collective conscience, as we search for answers. We'll look at the photograph of Adam Lanza and ask over and over again how he could have come to such a deadly crossroads.

We still know nothing about his motives, only the devastating carnage he wrought. And yet we've already heard from experts who talk about mental illness, Asperger's syndrome, depression, and autism . The chorus of gun boosters has defensively chimed in about how gun control would not have prevented this

Former Arkansas Gov. Mike Huckabee offered the theory that since "we have systematically removed God from our schools, should we be so surprised that schools would become a place of carnage?" (As if those heathen children deserved it?)

All the while, we continue to miss other crucial variables -- even though they are staring right back at us when we look at that photograph. Adam Lanza was a middle class white guy.

If the shooter were black and the school urban, we'd hear about the culture of poverty; about how inner-city life breeds crime and violence; perhaps even some theories about a purported tendency among blacks towards violence.

As we've seen in the past week, it's not only those living on the fringes of society who express anger through gun violence.

Yet the obvious fact that Lanza -- and nearly all the recent mass murderers who targeted non-work settings -- were middle class white boys seems to barely register. Look again at the pictures of Jared Lee Loughner (Tucson), James Eagan Holmes (Aurora) and Wade Michael Page (Oak Creek) -- a few of the mass killers of the past couple of years. (Yes, the case of Seung-Hui Cho, the perpetrator at Virginia Tech, the worst school shooting in our history, stands out as the exception. And worth discussing.)

Why are angry young men setting out to kill entire crowds of strangers?

Motivations are hard to pin down, but gender is the single most obvious and intractable variable when it comes to violence in America. Men and boys are responsible for 95% of all violent crimes in this country. "Male criminal participation in serious crimes at any age greatly exceeds that of females, regardless of source of data, crime type, level of involvement, or measure of participation" is how the National Academy of Sciences summed up the extant research.

How does masculinity figure into this? From an early age, boys learn that violence is not only an acceptable form of conflict resolution, but one that is admired. However the belief that violence is an inherently male characteristic is a fallacy. Most boys don't carry weapons, and almost all don't kill: are they not boys? Boys learn it.

They learn it from their fathers. They learn it from a media that glorifies it, from sports heroes who commit felonies and get big contracts, from a culture saturated in images of heroic and redemptive violence. They learn it from each other.

In talking to more than 400 young men for my book, "Guyland: The Perilous World Where Boys Become Men," I heard over and over again what they learn about violence. They learn that if they are crossed, they have the manly obligation to fight back. They learn that they are entitled to feel like a real man, and that they have the right to annihilate anyone who challenges that sense of entitlement.

This sense of entitlement is part of the package deal of American manhood -- the culture that doesn't start the fight, as Margaret Mead pointed out in her analysis of American military history, but retaliates far out of proportion to the initial grievance. They learn that "aggrieved entitlement" is a legitimate justification for violent explosion.

The easy availability of guns is another crucial variable. After the terrible school shooting in Dunblane, Scotland , in 1996, Great Britain enacted several laws that effectively made owning handguns illegal in that country. The murder rate in the U.S. is more than three times higher than Britain.

And yes, boys have resorted to violence for a long time, but sticks and fists and even the occasional switchblade do not create the bloodbaths of the past few years. In 2011, more than 80% of all homicides among boys aged 15 to 19 were firearm related.

We need a conversation about gun control laws. And far more sweeping -- and necessary -- is a national meditation on how our ideals of manhood became so entangled with violence.

It's also worth discussing why so many of these young mass murderers are white. Surely boys of color have that same need to prove their masculinity, and a similar sense of entitlement to annihilate those who threaten it. Perhaps the only difference is that it seems to be nearly the exclusive province of white boys to so dramatically expand the range of their revenge and seek to destroy the entire world, not simply the person or group that committed the supposed offense. Perhaps. It's a conversation worth having.

I am not for a moment suggesting we substitute race or gender for the other proximate causes of this tragedy: lax gun laws, mental illness. I am arguing only that we can never fully understand it, unless we also add these elements to our equation. Without them, the story is entirely about him, the shooter. But the bigger story is also about us.

In the coming weeks, we'll learn more about Adam Lanza, his motives, his particular madness. We'll hear how he "snapped" or that he was seriously mentally ill. We'll try to explain it by setting him apart, by distancing him from the rest of us.

And we'll continue to miss the point. Not only are those children at Sandy Hook Elementary School our children. Adam Lanza is our child also. Of course, he was mad -- as were Eric Harris and Dylan Klebold, and Seung-Hui Cho, Jared Lee Loughner, James Eagan Holmes, and Wade Michael Page -- and the ever-longer list of boys and young men who have exploded in a paroxysm of vengeful violence in recent years. In a sense, they weren't deviants, but over-conformists to norms of masculinity that prescribe violence as a solution. Like real men, they didn't just get mad, they got even. Until we transform that definition of manhood, this terrible equation of masculinity and violence will continue to produce such horrific sums.