A convicted sex offender suspected of murdering three people in Idaho and abducting two children, one of whom was later found dead, is under investigation in the 1997 kidnapping and killing of a 10-year-old Beaumont, Calif. (search), boy, the Riverside County (search) sheriff said Wednesday.

Joseph Edward Duncan III (search), 42, is linked by a single fingerprint to the scene of the killing of Anthony Martinez (search), Sheriff Bob Doyle told a press conference in Riverside, 60 miles east of Los Angeles.

Duncan was arrested last month for investigation of bludgeoning to death three people at a home near Coeur D'Alene, Idaho (search), and kidnapping Shasta Groene (search), 8, and her brother Dylan, 9, on May 16. Duncan was seized when people at a restaurant recognized the girl with him. Dylan's body was later found in Montana.

Confirmation of the fingerprint match was received on Monday, the sheriff said.

"We're pretty confident that he's our suspect. ... This is huge," Doyle said. "We followed up 15,000 leads over eight years. You can imagine the elation that everybody has."

FBI agents involved in the Idaho investigation contacted Riverside authorities on July 14, and said Duncan mentioned the name Martinez and the general area.

"So they called us to say, 'hey, you guys have a case?"' Doyle said.

Investigators flew to Idaho to fingerprint Duncan. They tried to interview him but he refused to talk.

On April 4, 1997, Anthony was forced into a white car in the town of Beaumont as his friends watched. The children were playing when a stranger offered them a dollar to help find his lost cat. Sixteen days later a forest ranger found the boy's nude, bound body in a desert area about 70 miles to the east.

The kidnapper was described at the time as blue-eyed and mustachioed, but efforts to track him down proved fruitless despite the extremely high profile of the case. Before the end of that April, authorities had evaluated more than 100 people as suspects.

Anthony's kidnapping united Beaumont, a small town on Interstate 10 in the inland region east of Los Angeles. Yellow ribbons were tied to trees and thousands of fliers with sketches of the suspect were handed out.

After circling vultures led a ranger to Anthony's remains in Berdoo Canyon in the Indio Hills, residents of Beaumont wept and prayed, and authorities vowed to capture the killer.

"I know we're going to get this guy," then-Sheriff Larry Smith pledged at the time.

Duncan has been charged in Idaho with kidnapping and murdering Shasta's mother, Brenda Groene (search), 40, as well as the woman's son Slade, 13, and her boyfriend Mark McKenzie (search), 37, at their home outside Coeur d'Alene.

Idaho had charged Duncan with kidnapping Shasta and Dylan from the home, but the state dropped those counts in anticipation of the federal government charging him with kidnapping the two children and with killing Dylan.

Federal prosecutors have said they will file charges in the abduction of the children and Dylan's death.

Authorities have also said Shasta and Dylan were sexually assaulted.

While it is The Associated Press' policy not to identify alleged victims of sexual assault in most cases, the search for Shasta and her brother was so heavily publicized that their names are widely known.

Duncan was sentenced to 20 years in prison for sexually assaulting a 14-year-old boy in Tacoma, Wash., in 1980. The term was suspended and he was put into sex offender treatment at a state hospital, but 22 months later officials said the treatment wasn't working. He was resentenced in 1982

Authorities said Duncan was paroled in September 1994 and moved into a halfway house in Seattle.

Documents show he got a job as a phone solicitor for a publishing company; went to counseling and later got a second job with a small software company.

In September 1996, Duncan tested positive for marijuana during a routine urine test, and he was arrested, then released on parole again, records show. In March 1997, he again tested positive for marijuana use, records show. He disappeared with his girlfriend's car, according to parole reports.

He was captured and returned to prison in October 1997 and finally released in 2000.

At the time of his arrest, Duncan was a fugitive charged with molesting a 6-year-old boy in Minnesota.