A convicted sexual predator already facing capital murder in the death of a 6-year-old boy in 1981 was charged Friday with the murder of a second boy.

Kenneth Kasten Rasmuson was charged in March with one count of murder with a special circumstance allegation that he committed the crime during the commission of a lewd or lascivious act upon a child, the Los Angeles County District Attorney’s Office announced in a news release.

Rasmuson’s first alleged victim, Jeffrey Vargo, disappeared on July 2, 1981.

The boy left his house in Anaheim Hills on his bike to go look at a fireworks stand, according to the DA’s office.

His partially-clad body was discovered the next day by two workers at a Pomona construction site. The Los Angeles County Department of Coroner later determined Jeffrey had been strangled.

“The murder remained unsolved for decades until a DNA hit connected Rasmuson to the crime and he was arrested in March in Idaho,” according to the release.

While incarcerated, investigators were able to use DNA to link Rasmuson to the unsolved death of another 6-year-old boy in 1986, prosecutors said.

As a result, prosecutors amended the felony complaint to include a second capital murder charge as well as a special circumstance allegation of multiple murders, the release stated.

The second victim, identified as Miguel Doe, disappeared from just outside his home on April 8, 1986. His body was found later the same day in a wash in Agoura Hills. He had been stabbed, strangled and sexual assaulted, according to a release from the Los Angeles County Sheriff’s Department.

Rasmuson was a registered sex offender in Idaho who was convicted in Los Angeles and Santa Barbara counties on three counts of performing lewd or lascivious acts with a child under the age of 14 years, according to the Idaho state police’s online sex offender registry.

He was also convicted of kidnapping for the purpose of a sexual offense in L.A. County, the online record showed.

The convictions came on Dec. 17, 1981, in Santa Barbara County and May 21, 1987, in L.A. County.

In the Santa Barbara case, Rasmuson pleaded guilty to kidnapping and molesting a 3-year-old boy. The toddler, who had been abandoned in a deserted area, was found naked near a highway, the L.A. Times reported.

Rasmuson had “committed an atrocious sexual act upon the child, including  … anal penetration,” a deputy district attorney was quoted at the time as saying.

L.A. Superior Court Judge Robert T. Altman called the crime “cruel, vicious and callous as conduct can become” when he sentenced Rasmuson to the maximum 17-year-prision term,” the Times reported.

“It’s been the court’s experience that people who commit these offenses simply do not change,” the judge said at the time. “They ought to be locked up for as long as conceivably possible for the protection of society.”

If convicted on the current charges, Rasmuson faced the death penalty or life in state prison without the possibility of parole. The decision on whether to seek the death penalty would be made at a later date, prosecutors said.

Rasmuson was being held without bail.

He was due to be arraigned on the second murder charge on Oct. 28.