updated 7/26/2012 12:22:26 PM ET 2012-07-26T16:22:26

As young people, do mass killers leave a trail of clues as to their future behavior? Are there tell-tale signals to a shooting spree such as the one in Colorado that killed 12 people last week?

Psychologists says it's nearly impossible to accurately predict human behavior, although they do agree that parents, teacher and friends need to heed warning signs that can signal the possibility of extreme violence; signals like depression, changes in mood or personality, drug or alcohol abuse, or a change in school performance.

Paul J. Frick, professor of psychology at the University of New Orleans, and a specialist in treating psychotic youths, says that the best predictor of adult violence is violence or aggression as a young person.

"Most people who have killed have a history of hurting other people," he said. "The key is what sets them off to where they take it to such an extreme."

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On Monday, a San Diego attorney representing the parents of Colorado shooting suspect James E. Holmes would not say whether Holmes had a history of mental illness, nor would she discuss any aspect of the relationship between Holmes and his parents. Holmes' mother is a nurse, his father is a software engineer, according to the San Diego Union-Tribune.

"It's awfully hard to generalize about these things," said Lawrence Steinberg, professor of psychology at Temple University and an expert in the psychology of adolescent development. "Some (mass murderers) have long histories of depression, others don't. Right now, we don't know yet about this guy's (Holmes) history. Some of these are loners, and he has been described as a loner, but many don't. Some are criminally aggressive before committing these crimes, others are not."

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Colorado law enforcement officials say Holmes did not have any prior run-ins with the law, nor did he get in legal trouble in either high school in San Diego or at the University of California, Riverside, where he was an academic standout in neuroscience.

In early June, however, Holmes flunked a set of oral exams at the University of Colorado medical center where he was pursuing a doctoral degree. He then purchased an automatic weapon that he later used to kill 12 people and injure 58 at a movie theatre in Aurora, Colo., according to news reports.

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While Holmes may at first appear to have been a highly-functioning individual without any past legal blemishes, some experts say that impression may change as more information comes out about his past.

While a person's violent tendencies may not be immediately obvious, Frick explained snapping "usually requires them to be callous and unemotional -- maybe things happen that their anger builds up to where they don't care anymore."

Frick, like other psychologists interviewed, said that there isn't enough data on mass killers to make generalizations about the exact factors that cause their crimes. However, Frick, who studies children who exhibit psychotic and violent behavior, also notes that it's rare that violence comes from out of nowhere and there are usually some signs in childhood.

"People who are highly intelligent can get away with it more," he said. "They may be better at covering it up from parents or teachers."

With early intervention, these violent children can be treated before they grow up to kill as adults, he said.

"The earlier you can spot a child that is hurting others the better," he said. "There's never a point where they are untreatable, but it's harder."

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This kind of therapy varies from patient to patient but often involves getting either children or adolescents to control their impulses, to exhibit empathy for others and to start feeling guilt for certain actions, according to Frick.

"You try to look at the case and what are the risk factors they are showing," Frick said.

It's also important to stay in touch with teachers and counselors as children spend more of their time away from home, according to John Murray, adjunct professor of psychology at Washington College in Chestertown, Md.

"Any behavior that seems to any parent that it might be odd: being withdrawn or emotionally controlled, angry, those are all things that you want to pay attention to as a parent and start asking questions," Murray said.

"I would start small by asking questions of teacher and counselors and listening for their concerns. They can spot this unusual behavior even with tens of thousands of kids in their classes. Once they are mobile, you miss out on 80 percent of their day. But you know what they are like at home and you can begin to ask questions."

© 2012 Discovery Channel


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