Criminal experts believe fantasy, obsession and the desire for control may have driven suspect Jake Patterson to allegedly kidnap 13-year-old Jayme Closs and kill her parents.
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Patterson, 21, who is charged with two counts of first-degree intentional homicide, kidnapping and armed burglary, has not entered a plea.
"He was a perfectly nice kid," Jim Moyer, his grandfather, told ABC News. "Nobody will ever know what went on in his mind."
Although Patterson's own alleged motivations have not been specified, criminal experts have ideas, based on studies and other cases, on what could have driven him to kidnap Closs and murder her parents.
'They don't have the tools'
Experts say many factors can contribute to a man wanting to abduct a girl, and it's possible for the inclination to start early.
Former FBI agent and ABC News contributor Brad Garrett said, according to studies, "People who end up abducting kids or young adults start these obsessions or fantasies many times when they're in elementary school. And they don't have the tools to sort of deal with that. When they get older, the fantasies, obsessions and even the violence become much more explicit."
Garrett said many of these cases can also be linked to past abuse, although there have been no indications Patterson was abused. He said studies suggest 70 percent of people who commit abductions were abused as children, physically or psychologically, which can create a pattern of rage (this does not mean all people who are abused then go on to abuse others).
That pattern, Garrett said, can teach a person that rage and violence is how to maintain control, especially in a relationship.
And the prospect of kidnapping a more helpless person -- like a child -- and controlling their every action is "intoxicatingly powerful," Garrett said.
'An absolute obsession'
Patterson confessed to investigators that he targeted Closs after seeing her board her school bus; he didn't know her, but decided "that was the girl he was going to take," according to a criminal complaint.
Garrett said kidnappers like the suspect "are absolutely obsessed and driven with a fantasy to control and dominate a woman. And many times they target younger women... because they're easier to control."
Meanwhile, crime victims advocate John Walsh told "Good Morning America" children are most vulnerable to predators while they're going to school and heading home.
"He spotted her, and for whatever reason, her image kicked in his fantasy," Garrett said. "This was all about Jayme."
"He became obsessed with her," added Walsh, and "he planned this so thoroughly."
Patterson told investigators "he put quite a bit of thought into details of how he was going to abduct" Closs and went to her home twice before carrying out the crimes, according to the complaint. It says he also chose which gun to take and prepared himself and his possessions to avoid leaving DNA or being caught.
"You also have to look at this as an absolute obsession," Garrett said. "This is in his mind all the time... and as the fantasy becomes richer and more explicit, the more likelihood he's gonna act on it. And I think that's what happened with Patterson. He didn't all of a sudden in October of last year, one day have the fantasy and the next day go abduct Jayme. This is something that has been building up."
Patterson allegedly gunned down Closs' parents at the home on Oct. 15 and fled with the girl in the trunk of his car before police arrived.
'Totally and utterly dependent'
According to Garrett, Patterson is similar to other kidnapping suspects in regards to how he allegedly controlled his victim and threatened punishment.
Once Patterson reached his house in Gordon, Wisconsin, he told investigators he created a space under his bed for Closs, and when he'd leave the house, he'd put plastic totes, barbells and free weights around the bed so she couldn't escape, according to the complaint.
Closs told investigators that Patterson "would make her stay under the bed for up to 12 hours at a time with no food, water, or bathroom breaks," according to the complaint.
"It's difficult to hold human beings," Garrett said. "You can physically restrain them, but you also have to threaten them with bodily harm, injury to them or others, if they don't obey you."
Closs also said he once hit her "really hard" when she tried to get out from under the bed and threatened harsher punishment if she tried again, the complaint said.
Patterson was likely "thrilled with what he had," Garrett said, which was a young woman "he can completely dominate, control, subdue, do anything to ... and basically keep her away from anybody else where there's no competition for basically interaction with her. In other words, she's totally and utterly dependent on him to survive."
'Heroic actions of the victims'
According to Garrett, it's usually "the heroic actions of the victims that end these cases."
Closs told investigators that Patterson left the house on Thursday and told her he'd be gone for five or six hours, according to the complaint. Closs said she pushed the bins and weights away from the bed and crawled out, making her break for freedom, according to the complaint.
Closs approached a woman walking her dog to plead for help, and the dog walker took Closs to a neighbor who called 911.
"This girl went through unbelievable trauma," Walsh said of Closs, adding, "she is one of the bravest victims we've ever been involved with."
"She not only escaped, she identified her perpetrator," Walsh said.
Patterson made his first appearance in Barron County Circuit Court on Monday where he was held on $5 million cash-only bail. He is due to return to court on Feb. 6.
ABC News' Bill Hutchinson and John Capell contributed to this report.