From age 6 to 13, when children are developing their skills and value systems, they are busy with social activities such as sports or playing an instrument.
"These pre-psychopaths are not doing that," said Dorr. "They are prowling and trolling, looking for something to get into. They are not normal, busy kids. ... They are finding short cuts to success."
Researchers don't know why.
"We look at fine families and one comes out to be a psychopath," he said. "And the one raised in the slums comes out a good person and gives back to the world."
One of the most infamous youth psychopaths was Eric Harris, the teen who opened fire at Colorado's Columbine High School in 1999 with his depressive friend, Dylan Klebold, killing 13 and injuring 24. Both killed themselves afterwards.
Experts interviewed by ABCNews.com on the 10th anniversary of the Columbine shootings in 2009, said that can't predict which teens will go on a suicide-driven rampage.
"Not all psychotics or psychopaths are going to kill and most are not dangerous," said veteran FBI behavioral scientist Kenneth V. Lanning.
In 2000, the National Institute of Justice joined forces with the Secret Service and the Department of Education to assess ways to prevent school shootings. It looked at 37 incidents to find patterns in school-aged assassins, concluding that all are male and most are loners with some kind of grievance. More than half had revenge as a motive.
"But that's typical of almost every adolescent," said Lanning.
Harris was described as controlling, manipulative and sadistic, but very much in touch with reality.
"Psychopaths don't feel guilty because they are blind to guilt," said Frank Ochberg, a former FBI psychiatrist who led the counseling team after Columbine.
Often, they are well-liked and charming and can be "wheeler-dealers and manipulators," he said.
In fiction, they are self-focused characters like J.R. Ewing from television's "Dallas" and Scarlett O'Hara from "Gone With the Wind."
When raised in a nurturing family, they tend to be thrill-seekers -- race car drivers and mountain climbers.
"They see themselves as victims, not telling the truth, avoiding, changing the truth around," according to psychologist Dorr. "They have a deficiency of anxiety. We would be nervous if we messed up. They are so cool, they can do dangerous things. And when they are caught, they are very smooth and don't feel guilty, and talk themselves out of it."
He also warned that parenting styles that are too permissive or too authoritarian can encourage a budding psychopath, who needs structure, limits and not aggression.
"Authoritative parents who are warm and provide support seem to lead the best," said Dorr.
Sometimes, with early intervention, teens can be helped in cognitive therapy to help them get out of their narcissism or self-centeredness.
"But it's tricky to diagnose," he said, "especially for parents."