A registered sex offender was busted in Idaho on Friday after forensic evidence linked him to the murder of a 6-year-old California boy over three decades ago.

Kenneth Rasmuson, of Sandpoint, is awaiting extradition to California to face murder charges for the death of Jeffery Vargo, who was missing for just one day before he was found dead at a construction site in his home city of Pomona, in 1981, according to the New York Daily News.

That was the same year Rasmuson was registered as a sex offender following his conviction for lewd and lascivious acts with a California child under the age of 14. The victim was 11.

Jeffrey Vargo, 6, vanished in July 1981 after leaving his home with his bike to visit a nearby fireworks stand. When he did not return, his parents went to the stand and found his bike abandoned in an alley, police said according to the Daily News.

He was found the next day, strangled to death, a coroner said at the time. The case remained unsolved for nearly 34 years until DNA evidence recently linked Rasmuson to the crime scene.

Rasmuson ended up in Idaho in 2010 after serving a 17-year sentence for abducting and sexually assaulting a 3-year-old boy and leaving him abandoned on the side of a highway, the Los Angeles Times previously reported.

"It's been this court's experience that people who commit these offenses simply do not change," sentencing Judge Robert T. Altman said of the defendant back in 1987.

"They ought to be locked up for as long as conceivably possible for the protection of society."