Guilty of one murder, charged with another and linked to two more slayings, Gary Michael Hilton appears poised for infamy.

While he doesn't yet qualify as a "serial killer," the Atlanta-born transient captured the attention of FBI profilers within a week of his arrest for the decapitation of Buford hiker Meredith Emerson. They traveled from headquarters in Quantico, Va. to observe Hilton during questioning and again when he pleaded guilty Jan. 31 to the murder of Emerson, whom he abducted from Blood Mountain in North Georgia on New Year's Day.

If the evidence against Hilton — he was charged Thursday in the decapitation of Crawfordville, Fla. nurse Cheryl Dunlap — leads to more convictions, their research has only just begun.

In anonymity, Hilton, 61, existed on the margins, drifting through a series of failed relationships, odd jobs and shiftless scams. The Army veteran never adapted to civilian life, often retreating to his van in the woods.

No longer anonymous, Hilton remains an enigma. His advanced age breaks the profiler mold, as serial murderers typically begin killing between 25 and 35 years of age, experts agree.

"This guy didn't just fall off the turnip tuck and start doing this," said retired FBI profiler Clint Van Zandt.

Criminologist Eric Hickey, director of forensic studies at Alliant International University in Fresno, Calif., said he expects Hilton's predatory behavior began well before October 2007, when the Army veteran is alleged to have abducted and murdered avid hikers John and Irene Bryant. Transylvania (N.C.) County Sheriff David Mahoney said there is "no question" Hilton was responsible for the elderly couple's deaths.

"It's almost unprecedented to see someone go from zero to what he did," Hickey said. "I'd suspect he could be linked to several other crimes."

Officials in Pickens County, S.C., are waiting until North Carolina completes its investigation of Hilton before pursuing him as a possible suspect in the abduction of Clemson University student Jason Knapp, last seen on Easter 10 years ago. Investigators said Knapp's fingerprints were on a ticket admitting him to Table Rock State Park.

Noel Talley, spokeswoman for the North Carolina Department of Justice, confirmed Hilton is a suspect in Rossana Miliani's disappearance but declined to offer more details. Miliani was last seen Dec. 7, 2005 near Bryson City, N.C. Some said she was with a white man in his 60s, and the young woman appeared nervous.

Beyond his age, Hilton fits many of the characteristics shared by serial killers. Renowned criminologist Steven Egger's criteria include a minimum of two murders (though some experts say three killings are a better indicator), no relationship to the victim and no connection to the other crimes. The slayings typically occur at different locales (Hilton is linked to crimes in three states so far), though the victims often share characteristics such as gender or age. The motivation is not financial, Egger said, though Hilton told the GBI that's why he killed Emerson.

"Money was a secondary issue," Hickey said. "This was about power. When you consider his comfort in the woods, that is where he felt most powerful, and that's why he killed them where he did."

Why he killed them is the greater mystery. The Bryants' murders coincide with a relatively dramatic event in the killer's life, the loss of his only link to normalcy. In September 2007, his longtime employer, John Tabor, succumbed to Hilton's demands for $2,500. Hilton's behavior had become increasingly erratic, Tabor said, and he paid him off in hopes of severing their already fractured relationship.

"This is systemic behavior with most of these guys," Hickey said. "He feels like the world is against him. There's issues of rejection, abandonment. Killing becomes his focus."

But Hilton got sloppy, especially in disposing of clues linking him to Emerson's death. He was arrested at a Chamblee convenience store near a busy intersection after being spotted dumping loads of sleeping bags, backpacks, bedrolls and blankets into a dumpster.

"Narcissism is not uncommon for such antisocial personality disorders," said Joe Davis, a veteran profiler and forensic psychologist based out of San Diego. "He likes the attention he's getting."

And while all the bodies were dumped within dense forests, they were still somewhat conspicuous. (Hilton led authorities to Emerson's body on the condition they not seek the death penalty.) Hunters in Florida and North Carolina, respectively, discovered Dunlap's and Bryant's corpses mere yards from unpaved hunting trails.

"I suspect he wanted them to be found," Hickey said. "He wants to be heard. He wants to frighten people. He wants to show his power. To him, it's really about having a voice."

While there's widespread speculation that Hilton has killed before, veteran GBI agent John Cagle, who led the investigation of Emerson's murder, said he has little doubt Hilton would've continued killing had he not been captured.