A Michigan woman is making it her life's mission to help foster children and families since she learned the fate of her own biological mother, who was murdered by two notorious California serial killers in the mid-1980s.

Cheryl Gyant's mission to know her mother began at 10 years old, when her grandmother told her she was adopted. 

"I was dealing with that internally, and it was such a struggle," recalled Gyant, who wrote a book based on her experience, "A Letter from Sheri." She didn't want to ask her adoptive parents, whom she loved and who loved her, about her biological parents for fear of offending them.

"I remember being little and being at the grocery store with my mom and just looking at people — looking at women and saying, ‘I wonder if that’s my mom,'" she said.

BTK SERIAL KILLER NOT INVOLVED IN OKLAHOMA COLD CASE, DAUGHTER SAYS, DESPITE REPORTS HE WAS QUESTIONED IN PRISON

Cheryl Gyant wrote a book, "A Letter from Sheri," based on her mother's life and early death. (Cheryl Gyant)

Authorities found and recovered her mother Sheryl Okoro's remains, including a neck bone and three leg bones, at a rural Wilseyville, California, property at the base of the Sierra Nevada.

VERMONT COLD CASE MURDER SUSPECT FLED COUNTY, BECAME MONK AFTER SRANGLING WOMAN

Serial killers Leonard Lake and Charles Ng used the property to rape, torture and kill as many as 25 women, men and babies they abducted in the mid-1980s as part of a sick serial killer fantasy. The killers hid and attempted to burn victims' bodies on the property.

Lake and Ng also hid some of the victims in a bunker near the Wilseyville property. Lake had a fantasy of holding women captive for some 20 years before he carried out the crimes.

Charles Ng's serial murder trial ended with a guilty verdict in 11 of 12 murder counts against him.  (Don Kelson/Los Angeles Times)

An investigation into their crimes lasted nearly five weeks, according to court documents, during which time investigators "discovered thousands of bone and tooth fragments buried throughout" Lake's and Ng's property.

"At least four dental specimens belonged to a child under the age of three years old. After reviewing all the found fragments, two forensic anthropologists concluded that they belonged to at least four adults, one child, and one infant. ‘Many hundreds’ of the bone fragments showed various degrees of burning. Investigators also found a child’s liver buried on the property," a Calfiornia Supreme Court filing states.

AUBURN UNIVERSITY STUDENT'S REMAINS ID'D NEARLY 50 YEARS AFTER HE DISAPPEARED BUT MYSTERY CONTINUES

Okoro had three daughters before her death at age 26, including Gyant, who was adopted by a Grand Rapids, Michigan, couple in the 1970s. Gyant finally learned her mother's fate in 2002, when her aunt reached out to her and "confirmed" that her mother was "murdered by serial killers in California." 

An investigation into their crimes lasted nearly five weeks, according to court documents. Investigators "discovered thousands of bone and tooth fragments buried throughout" Lake's and Ng's property. (Mike Maloney/San Francisco Chronicle)

Her aunt then gave her the business card for a detective, who informed Gyant of an 11-page letter her mother had written that authorities recovered from the crime scene. 

The letter detailed a grueling childhood, upbringing and early adulthood that was eventually stolen from Okoro when she was murdered.

GEORGIA AUTHORITIES FIND HUMAN REMAINS THAT MAY BELONG TO COLLEGE STUDENT MISSING FOR 45 YEARS

Okoro said she was sexually abused by her parents and strangers as a child and turned to a life of prostitution later on in life.

Sheryl Okoro said in her letter that she was sexually abused by her parents and strangers as a child and turned to a life of prostitution later on in life. (Cheryl Gyant)

"Oh my God. … I had no preparation," Gyant said of reading her mother's letter for the first time. 

When Okoro went missing in the 1980s along with more than a dozen other people connected to the serial killer case, Okoro was dismissed as a prostitute rather than one of Lake and Ng's murdered victims, Gyant said.

IDAHO MURDERS: DAUGHTER OF BTK KILLER ‘WOULDN’T BE SURPRISED' IF SUSPECT CONTACTED HER FATHER

"She was killed by a serial killer, and she's listed in the investigation as a prostitute. And, by the way, no one got charged in her murder," Gyant said.

When Okoro went missing in the 1980s along with more than a dozen other people connected to the serial killer case, Okoro was dismissed as a prostitute rather than one of Lake's and Ng's murdered victims, Gyant said. (Cheryl Gyant)

Authorities will again test Okoro's bones found at the scene, including a neck bone and three leg bones, to confirm her identity. They have also asked Gyant to submit DNA in an effort to help.

Calaveras County investigators reopened the case in August 2021 to test DNA evidence again.

"Through this project, the Calaveras County Sheriff’s Office is seeking to bring closure to the victims’ next of kin by potentially identifying their loved ones’ remains," the sheriff's office said in an Aug. 23, 2021, press release. "At the conclusion of the analysis, remains will be held as legally necessary, returned to loved ones or re-interred."

Calaveras County investigators reopened the case in August 2021 to retest DNA evidence. (Mike Maloney/San Francisco Chronicle)

"Now … that DNA is more sophisticated, they're going back and testing all of these bones, and they have tons of them," Gyant said.

The letter also detailed Okoro's efforts to ensure Gyant was adopted by the right family when she was just 16 years old because Gyant is mixed-race, and Okoro did not feel her family would accept a mixed-race baby.  

Gyant now wants to pay tribute to her mother by helping other foster children and families through her nonprofit, the Shania Rose Community Development Corporation.

CLICK HERE TO GET THE WHD News APP

The cover of Cheryl Gyant's book based on her mother's life and death, "A Letter from Sheri." (Cheryl Gyant)

Okoro's full letter can be found in Gyant's book, "A Letter from Sheri," which is available for purchase on Amazon.

Lake died by suicide in 1985 after police found items belonging to the missing victims in his vehicle. Ng was sentenced to death at San Quentin State Prison.