"We are hoping they can give us some information that we haven't found yet," Oklahoma State Bureau of Investigation spokeswoman Jessica Brown told AOL News. "They are the experts in behavioral analysis. We do not have that expertise, so that is why we are going to them."
"You get to a point in the case where you are looking for help in any manner," Brown said.
The bodies of Taylor Paschal-Placker, 13, and Skyla Jade Whitaker, 11, were found on June 8, 2008, in a ditch along County Line Road in Weleetka.
According to the Okfuskee County Sheriff's Office, Skyla had been spending the night at Taylor's house, and the two had decided to take a walk along the dirt road.
When the girls failed to return home, Taylor's grandfather, Peter Placker, went looking for them. He walked roughly a quarter of a mile down the road before discovering the girls' bodies, police said.
According to autopsy reports, Skyla had been shot a total of eight times in the neck, arms, shoulders, chest and abdomen. Taylor had been shot five times, in the face, groin and hand.
The county coroner found no signs of sexual assault, but he did find that each of the girls had been shot with two different caliber bullets. Investigators believe a .40-caliber handgun and a smaller-caliber weapon were used in the killings. Authorities have declined to release any other information on the weapons.
Investigators have checked out hundreds of leads and identified several persons of interest in the past two years, but they have been unable to determine who is responsible for the murders, Brown said.
"We have looked at similar crimes [but] we haven't found any in Oklahoma, necessarily," Brown said. "We have also looked throughout the country ... [but that] hasn't produced a lot of helpful leads."
While an FBI profile cannot be used as evidence in the case, it can be used to help police identify potential suspects, former FBI agent Harold Copus told AOL News.
"You need more than a profile to get a search warrant or make an arrest," said Copus, now head of Copus Security Consultants in Atlanta. "A profile is a road map that leads you from a crime scene to the potential perpetrator. Then, once you identify a suspect, you have to do all the work of making the case. But it certainly shortens the road map of how to get there."
According to Copus, agents in the FBI's Behavioral Science Unit have spent years studying psychology and interviewing hundreds of killers around the country. The profilers use their knowledge to determine how killers think and operate.
"Based on the case and similar crimes they have investigated, [a profiler] can determine a lot of different things about the psychological make up of this person or persons," Copus said. "The police can then go back in their interviews and possibly say, 'Wow, we missed this and we need to concentrate this person.'"
Copus added, "In my experience, the profilers are great at what they do. If I was the person who had done this, I would be shaking in my shoes knowing they are on top of me now."
Speaking with The Oklahoman today, Taylor's grandmother, Vicky Placker, said she is aware that the FBI has been asked to assist in the case.
"We just hope something comes from this," she said.
Brown is also hopeful that their assistance will ultimately result in an arrest.
"It is awful, and we are willing to do whatever it takes to get it solved, and the sooner the better, of course," Brown said.
When asked whether investigators fear the killer or killers could strike again, Brown replied, "Absolutely."
"If they are willing to kill two innocent children in cold blood, I don't think there [are] any limitations," she said.