One of San Joaquin County’s most notorious serial killers, Wesley Shermantine, has died in prison.

Shermantine, 60, and his late accomplice Loren Herzog became known as the “Speed Freak Killers.” Together, they fatally shot and stabbed on young Stockton women, not to mention drifters, fellow drug abusers and others unlucky enough to have crossed their paths. The exact number of homicides they committed never was fully determined but is possibly 19 and could be as high as 72. Both were arrested for murder in 1999.

Shermantine was serving his sentence for murder at California State Prison, Sacramento, one of 564 Death Row inmates. The cause of his death on Sept. 17 was under investigation, according to the California Department of Corrections and Rehabilitation.

District Attorney Ron Freitas took note of Shermantine’s victims.

“Today, our hearts are with the families of Cyndi Vanderheiden, Chevelle ‘Chevy’ Wheeler, Howard King III, Paul Cavanaugh, and everyone whose lives were shattered by the ‘Speed Freak Killers,’ ” said Freitas in a statement. “For decades, these families have carried a heavy, unbearable grief. While Wesley Shermantine’s death marks the final chapter of his legal sentence, it doesn’t erase the pain left behind.”

Shermantine and Herzog grew up in Linden and became known for criminality and drug use as early as high school. They also were known as methamphetamine users — hence the nickname — though the depth of their criminal activity wouldn’t become known for about more than a decade when they were connected to a murder.

The murder that broke open the case was of Vanderheiden, who lived in Clements. Blood was found in Shermantine’s car that matched the victim’s. In the ensuing investigation, police quickly also focused on Herzog as well.

It was then that Herzog spilled the beans about other killings — men and woman alike. Shermantine was convicted of four murders in 2001, including Wheeler, who disappeared in 1985 from Franklin High School in Stockton.

Herzog was sentenced to 78 years in prison, but was released in 2010 on parole after his murder convictions were overturned on appeal and he pleaded guilty to lesser charges. He committed suicide two years later, about the same time Shermantine started disclosing where victims’ bodies were buried. Authorities initiated a series of digs, finding bone fragments linked to victims in some and nothing in others.