Sex offender linked to another killing

RIVERSIDE, Calif., Aug. 4 (UPI) -- A convicted sex offender charged with kidnapping two Idaho children after killing their family reportedly has admitted to an 8-year-old slaying.

Joseph Edward Duncan III, 42,confessed to killing Anthony Martinez, a California boy whose 1997 abduction triggered one of the Inland area's biggest manhunts, a source close to the investigation said.

Duncan, who has not been charged in the Martinez case, told FBI agents in Idaho he crushed the boy's head with a rock, the source told the Inland Southern California Press Enterprise. Duncan's thumbprint reportedly was found on duct tape on the victim.

Riverside County Sheriff Bob Doyle says investigators are "pretty confident" Duncan is guilty.

Duncan was arrested in July in the May 16 bludgeoning deaths of Brenda Groene, 40; her son, Slade, 13; and her boyfriend, Mark McKenzie, 37, near Coeur d'Alene, Idaho.

He allegedly kidnapped Shasta Groene, 8, and her brother Dylan, 9, whose body was found in Montana.