FRENCH CAMP, San Joaquin County (CBS / AP) -- Two more possible victims of the "Speed Freak Killers" were identified Friday—more than 25 years after the teens disappeared from their Stockton homes, authorities said.
The disclosures bring to four the number of missing young women from the Central Valley whose remains have been found this year as the result of a death row inmate's crudely drawn maps directing authorities to burial sites.
In the latest discovery, San Joaquin County Sheriff Steve Moore said the remains of Kimberly Billy, who went missing in 1984 at the age of 19, and JoAnn Hobson, who disappeared in 1985 at 16 were among the hundreds of bone fragments found last month in an abandoned well near the farming town of Linden.
Authorities were working to identify the remains of a third body found in the well.
"At this point, of those 1,000 bone pieces that were recovered from the well, the forensic anthropologist has been able to reconstruct what they believe to be three individuals," Moore said.
Investigators believe they were victims of Wesley Shermantine and Loren Herzog, who authorities say went on a methamphetamine-fueled killing spree in the 1980s and 90s.
"We are shifting gears," Moore said at a news conference in French Camp, "from missing persons cases to homicide cases."
Searchers were directed to the well by Shermantine, who hand-drew maps in his San Quentin Prison cell after a Sacramento bounty hunter promised to pay him for information about victims.
Authorities unearthed the remains of two other young women in February who were believed to be the victims of Shermantine and Herzog—two childhood buddies.
Shermantine is now on death row for four murders. He sent authorities on a massive search after he agreed to disclose burial locations in exchange for $33,000 from the bounty hunter. Herzog hanged himself in January after the bounty hunter told him Shermantine was disclosing locations of victims, including the Linden well that Shermantine described as "Loren's boneyard."
Investigators were still analyzing evidence found in the well and were working to identify more possible excavation sites.
"This is a very long process," Moore said.
Billy was last seen on Dec. 11, 1984, and her grandmother reported her missing two weeks later after she failed to contact any family members over the Christmas holiday, according to sheriff's officials.
Hobson was last seen in her east Stockton neighborhood on Aug. 29, 1985. Investigators have long suspected Shermantine and Herzog in the girl's abduction and death, but they never had enough evidence to charge them.
Hobson' mother, Joan Shelley, emotionally declined comment when contacted by phone Friday.
During last month's search, authorities combed a remote Calaveras County property once owned by Shermantine's family and excavated an abandoned well near the farming town of Linden.
At the Calaveras County property, they found the remains of Cyndi Vanderheiden, 25, who disappeared in 1998, and Chevelle "Chevy" Wheeler, 16, who disappeared in 1985.
Shermantine was convicted of both murders in 2001. He was arrested in 1999 after his car was repossessed and investigators found Vanderheiden's blood in the trunk. Using a new collection technique not available in 1985, they also found Wheeler's DNA in a remote Calaveras County cabin owned by Shermantine. The cabin was near the site where Wheeler's body was found.
Shermantine was also convicted of robbing and killing two drifters as they sat in a car in a rural area about two miles west of Stockton. Tire tracks left at the scene matched those of a red pickup Shermantine drove at the time.
Herzog's three, first-degree murder convictions and 78 years-to-life prison sentence were tossed by an appeals court, which ruled his confession was illegally coerced. He later pleaded guilty to voluntary manslaughter in Vanderheiden's death and was paroled in 2010 to a government-owned trailer outside the walls of the Susanville prison.
Shermantine, who blames Herzog for the killing spree, told authorities that 10 or more bodies could have been stashed at the Linden well. Searchers dug up hundreds of bone fragments, as well as purses, shoes, jewelry and other evidence.
Before his suicide, Herzog maintained Shermantine was responsible for the deaths.
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