A loner with a grudge and a penchant for odd philosophy shoots an Arizona congresswoman, a federal judge and a roster of other victims outside a Tucson supermarket. The penetrating gaze and eerie smile in the gunman's mug shot bring to mind other headline makers – criminals who leave us scrambling to understand and stem their violent outbursts.

Some commentators and bloggers blame our current political climate for the Arizona atrocity. While I am as appalled as the next person by a lack of civility in our political discourse, politicians were not the ones wielding guns in Arizona. So what motivates violent behavior? Can it be prevented?

Mass murder is not predictable, and no single personality trait, physiology or background factor makes violent behavior inevitable. But research has identified several factors that make violence more likely. Some of these are factors you and I can do something about.

First, perpetrators of violence often see other people as objects. Their feelings, dreams and relationships are invisible or irrelevant. Neglect or abuse, during which children are treated as such objects, is one factor in developing this mind-set.

Consider the thought processes of forger and murderer Mark Hofmann, whose letter to his parole board was recently released:

"I believe I was trying to convince myself of the worthlessness of life and of life's unfairness. I told myself that my survival and that of my family was the most important thing."

As he rationalized murder to avoid detection of his forgeries, Hofmann told himself that his intended victims might just as easily die from an accident or natural disaster. Their lives became inconsequential while the preservation of his reputation became paramount.

Second, the violent may lack skill in defusing their anger. They see small slights as sufficient disrespectful or threatening to justify rage. They blame others for their problems, obsess over perceived insults and injustices, and combat resulting feelings of powerlessness with fantasies of revenge. For example, there is speculation that Congresswoman Gabrielle Giffords' assailant felt so slighted when she brushed off his question at an earlier event that he began plotting against her.

Third, judgment in the violent may be compromised by their biology. Certain genes have been implicated in violence when coupled with childhood neglect or abuse. When prefrontal lobes (responsible for impulse control, judgment, planning, reasoning, calming, and empathy) are slow to develop aggression is more likely, and at best, prefrontal lobes don't completely mature until the early 20s.

Alcohol or drugs further impair judgment and loosen inhibitions. Serial killer Ted Bundy blamed alcohol for lowering his inhibitions and lighting the match to his violent interests.

Fourth, the violent may lack social connections and feel misunderstood and alone. Most individuals who lack social skills or suffer from mental illnesses do not becoming violent, and most awkward or impulsive kids grow out of it.

In combination with other factors, though, feeling alone, misunderstood or rejected can fuel fantasies of using violence to become famous or get even. Timothy McVeigh, the Oklahoma City bomber, apparently hit a breaking point that turned toward violence over repeated romantic rejections.

Fifth, certain aspects of the environment and culture make violence more likely. Research suggests that high rates of violence in the United States are fueled by a large disparity between rich and poor, high mobility and individuality and weaker community ties, glorification of and access to weapons, and unremitting media violence and pornography portraying people as disposable objects.

For example, in a widely publicized interview granted hours before his execution in 1989, serial killer Ted Bundy said, "Those of us who have been so influenced by violence in the media, particularly pornographic violence, are not some kind of inherent monsters. We are your sons and husbands. We grew up in regular families. Pornography can reach in and snatch a kid out of any house today. It snatched me out of my home 20 or 30 years ago. As diligent as my parents were, and they were diligent in protecting their children, and as good a Christian home as we had, there is no protection against the kinds of influences that are loose…. I've lived in prison for a long time now, and I've met a lot of men who were motivated to commit violence. Without exception, every one of them was deeply involved in pornography. "

In the decades since Bundy committed his crimes, internet and media have exponentially expanded access and exposure to pornography and violence of every combination. Although biology, upbringing, temperament or culture alone does not unerringly produce violence, the wrong combination can turn lethal.

How can we reduce the odds of that lethal chemistry reaching a flashpoint?

1. We can help kids develop empathy by showing them empathy, teaching them to serve and help others, and helping them imagine others' feelings. A young man tempted to sexual violence against women he saw as "whores" had a breakthrough of empathy when he answered the question, "How do you think God sees these women?" with "They are his daughters; He loves them."

2. We can learn, teachand model good anger management skill, including talking ourselves and others down instead of fueling rage when slighted by a boss, cut off on the freeway, or at odds with a politician.

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3. We can do more to protect children and teens from alcohol, drugs, and abuse, giving their prefrontal lobes time to mature. This includes getting them involved in healthy activities where they develop talents, stress management skills and self-esteem.

4. We can expose children to family members or others who are disadvantaged, odd, or different and help them make a connection. We can teach social skills in school and work settings. We can reach out to at least one person who is difficult to like.

5. As a society we can insist on limits on pornography, especially violent pornography, in the media and Internet. We can do more as parents to monitor cell phones and computers and explain why. We can work to reduce economic disparities and decrease materialistic displays. We can foster community ties with new neighbors and extended family. Anger, vengeance and fighting may be part of human nature, but we can fight back.

Wendy Ulrich, PhD, MBA, psychologist, author, and founder of Sixteen Stones Center for Growth (sixteenstones.net), most recently co-authored the New York Times bestseller "The Why of Work."