Ayres' body, marred by 36 wounds on the head and torso, was found near a dump site adjacent to a soccer field not far from Headley's Southampton home.
Robin Sabel of Mount Holly gets chills when she recalls how her daughter Heather, then 16, dated Headley when he was 22.
"When we first met him, he was very quiet, kind of kept to himself, had nice manners, and I think it was because he was raised by grandparents," Sabel said in an interview last week.
"But when I saw the other side of him, it was scary," she said, noting that Headley tried to choke her daughter when the teenager tried to break up with him. The family attempted to get a restraining order against Headley, Sabel said.
New information about Headley's case recently came to light in a brief in which Assistant County Prosecutor John Brennan asked state Superior Court Judge James Palmer Jr. to reconsider his preliminary intent to sentence Headley to 30 years, the minimum for murder. The deal was in exchange for a guilty plea.
Palmer reversed himself on Nov. 7, saying his review of the records had convinced him a longer sentence was appropriate. The judge also received a two-inch-thick pile of petitions and letters from the victim's family and supporters, urging him to sentence Headley to life.
Palmer revoked Headley's plea and a trial date is tentatively set for February.
Headley's mother, Cammy, summoned police hours after the killing. Her son confessed and told her "he had blacked out and that's when he grabbed the knife from somewhere . . . and stabbed [Ayres]," she told authorities.
Headley's sister, who was in the room when he allegedly recounted the attack, asked why he had done it. He said he didn't know, according to his mother's statement.
When Headley saw that his mother was calling police, he ran out, saying, "I deserve to die; I took a life," she told officials. He headed for the highway and was hit by a truck.
While in the hospital with fractured ribs, Headley told state police his friend Steven Kemmerer had introduced him to Ayres a couple months earlier at a party, according to court records. Headley said he later met her at a convenience store in Medford. He got into her Mustang and they talked, he told police, but he couldn't recall what happened next.
The next day, he asked for a lawyer.
Kemmerer, 25, of Burlington, told police his friend had issues with women.
"He comes off as a nice guy in the beginning and turns into a creepo after that," Kemmerer said. He would wait until "girls could be comfortable with him," then come on "really strong."
Headley had graphic "fantasies of killing people" and often threatened to stab or shoot people he had argued with, according to Kemmerer, who was arrested in Willingboro over the summer on a theft charge.
Ayres' cousin Kellie Lando said her family believed Ayres thought she was meeting Kemmerer after she got a text from his phone on Sept. 13. She had gone out with Kemmerer a few times, Lando said, and Headley sometimes used his friend's cellphone.
Ayres was All South Jersey while playing softball at Deptford High and 2007 Atlantic 10 Rookie of the Year while at Fordham University. She was a pitcher.
Headley, who also had played softball, would frequent a local skating rink and sometimes took women to a secluded area near the soccer field where Ayres' body was found, Raine Terry of Mount Holly, a friend, told authorities.
"Normally, he's cool, calm, and collected. But he does have anger problems," Terry said.
Cedric Edwards, Headley's public defender, said last week his client's friends were "embellishing their stories" and should not be believed.
He acknowledged that Headley - who he said was from a troubled family and has a learning disability and history of depression - had been in trouble in the past.
While in custody, Headley told psychiatrists he had experimented with drugs but did not abuse them or alcohol, according to court records. The doctors could not determine whether Headley was depressed, but they did not think he needed to be admitted to a mental hospital.
When they asked whether he had a girlfriend, he replied, "No, they cost too much."
In the past, Headley had violent fights with his mother and sister and was taken several times to a crisis intervention center for evaluation.
In 2004, he was convicted of endangering the welfare of a child after kissing and fondling an 11-year-old girl at a skating rink when he was in his 20s. He was placed on probation.
He currently is in the Burlington County Jail with bail set at $750,000.
Contact Jan Hefler at 856-779-3224, firstname.lastname@example.org, or follow on Twitter @JanHefler. Read her blog, "Burlco Buzz," at www.philly.com/BurlcoBuzz.