Most mass shooters share one very commonplace trait: Anger

More than 15 years before Wednesday's mass shooting at the VTA light rail yard in San Jose, the man identified by police as the shooter Sam Cassidy, 57, had expressed anger and a desire to harm his colleagues according to his ex-wife. 

"His ex-wife...(said) that Cassidy had a bad temper and would tell her that he wanted to kill people at work," Cecilia Nelms told the Associated Press on Wednesday. Nelms said they divorced in 2009 after being married for 10 years. She said Cassidy had been treated for depression and she had felt scared at times when he lost his temper.

"He would get more mad...he could dwell on things," Nelms said. "I never believed him, and it never happened. Until now."  

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While some people might portray mass shooters as monsters or having a mental illness that makes violence impossible to prevent, a recent study suggests that most mass shooters share one very commonplace trait.

"Most mass shootings are not random and senseless but involve anger," wrote a research team of psychologists led by Ephrem Fernandez, a clinical psychologist at the University of Texas-San Antonio who also serves as a visiting professor at UC Berkeley.

The research team analyzed 132 mass shootings from the Stanford MSA database that occurred between 2000 to 2015.

"In 70% of these cases of mass shootings, there was evidence of anger," said Fernandez, "What we're finding is that these are individuals who are experiencing an emotion that's actually quite commonplace and the difference, of course, being that they take it to such an extreme."

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Fernandez says in many shootings, the perpetrator's anger came from a sense of being wronged. The research study found 38% appear prompted by abandonment or rejection, and 34% by insults.

Often, however, signs of anger might be dismissed as just talk or blowing off steam. Fernandez says helping people find ways to address anger through anger management or taking action before it escalates, could help avoid violence.

Robyn Thomas, the executive director of the Giffords Law Center to Prevent Gun Violence, says there are community resources to support anyone who feels a gun owner might pose a serious threat of taking violent action.

"In California, we actually have, in addition to a gun violence restraining order and domestic violence restraining orders that many people are familiar with, we also have something called a workplace violence restraining order," said Thomas, "There are self-help centers at the courts, designed to help laypeople file the paperwork necessary. These are temporary restrictions on gun access."

SEE ALSO: Why did the gunman kill 9 co-workers at the San Jose VTA light rail yard before killing himself?

"I think it's really important to understand the purpose of these gun violence and workplace violence restraining orders. The intention of them is to have a temporary removal of guns," said Thomas. "You go to the courts. You file paperwork under oath stating what your concerns are and then there's an investigation and law enforcement can go and speak to people. They go in front of a judge and there's an opportunity to present the information in a way that complies with the system. So we're not looking to try and do this thoughtlessly, What we're looking to do is create a process that's really transparent."

Fernandez says he would like to see more assistance and support for people to learn to express and deal with their anger before it reaches a crisis point. Fernandez says his research team is exploring whether hotlines similar to suicide prevention hotlines might help in some cases.

"People, as angry as they may feel, are so afraid and reluctant about the consequences if they were to disclose anger," said Fernandez. "If only we could understand their anger, manage it, regulate it before it reaches that point of destructiveness, then we can say that we have done a better job than simply saying they're deviants and they're crazies."

Jana Katsuyama is a reporter for KTVU.  Email Jana at and follow her on Twitter @JanaKTVU or Facebook @NewsJana or