02/24/2012 07:21 pm ET Updated Feb 24, 2012

'Speed Freak Killers' Investigation Uncovers Another Body

Investigators in northern California discovered another set of human remains Thursday in an area where victims of the 'speed freak killers' were found earlier this month, authorities said.

The remains represent at least the fourth body discovered by investigators after Wesley Shermantine, the surviving member of the pair of serial killers active during the 1980s and 1990s, began providing directions to burial sites to a local newspaper reporter and a Sacramento bounty hunter earlier this month.

Shermantine, awaiting execution on San Quentin's death row, blames his accomplice, Loren Herzog, for all the murders and maintains that he only helped dispose of the bodies. The two men were dubbed the "speed freak killers" after a 15-year drug-fueled killing spree that ended with their arrests and convictions for multiple homicides in 1999.

Authorities charged them with six murders but suspected them of killing 20 or more. Only a few bodies of victims had been found at the time.

Herzog, released from prison in 2010 after his murder convictions were overturned on a technicality, killed himself in January after Shermantine agreed to provide directions to the burial sites. The two were childhood friends who grew up and lived in Linden, a small farming community.

The remains found Thursday have not been identified and are not mentioned by Shermantine in any of his letters, according to bounty hunter Leonard Padilla, who has received letters from Shermantine for years. They were near where the bones of two women, Cyndi Vanderheiden and Chevelle "Chevy" Wheeler, were discovered with Shermantine's help Feb. 8 and 9, according to Les Garcia, a spokesman for the San Joaquin County Sheriff's Office, which is leading the investigation.

A dog trained to locate decades-old human remains led searchers to the body, Garcia said.

All three remains were found near or on land formerly owned by Shermantine's family in Calaveras County. Investigators returned to the area Friday to continue the search for additional remains, Garcia said.

Padilla has offered the killer $33,000 to reveal the locations of more victims and, according to a letter from Shermantine to Padilla received Thursday, clues on the locations of undiscovered remains may be forthcoming.

In the letter, Shermantine pledges to provide maps and directions to two previously unknown burial sites, once he is paid for the information. "I will make a map to both soon as our deal is kept," he wrote. "I have proven I'm telling the truth all the way. Now it's your turn."

Padilla said he has sent a preliminary $2,000 check to Shermantine and will be providing the rest of the money soon.

After Shermantine sent Padilla a handwritten map and directions earlier this month, authorities excavated an abandoned well in rural San Joaquin and recovered 1,000 bones and bone fragments, including human skull fragments, as well as a woman's purse, shoes and jewelry.

But in the new letter, Shermantine says that another abandoned well nearby contains additional remains. "You've only found the well with one or two bodies in it," he writes. "Herzog (sic) other well has more."

Shermantine also wrote that there is "one more sight [sic] in Stockton" where Herzog "killed and left a woman between 1984-1985."

"I will be drawing up maps of both areas," he wrote.

Padilla said he had not yet spoken with Shermantine about the remains discovered Thursday, and that the killer made no previous mention of additional remains in the area.

"I've just gone along with what he's volunteered. We just listen," he said. "If he calls me back, I will probably ask him about it."

The latest letter to Padilla, dated Feb. 13, also notes the growing media frenzy surrounding the case. "Do I have their attention now!" Shermantine wrote.