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BOSTON — A decadeslong search for a fugitive charged in the 1980 killing of a Pennsylvania police chief came to a dramatic end Friday as authorities positively identified remains found buried in a Massachusetts yard as the man they have long suspected in the fatal shooting.

Donald Eugene Webb was one of the longest-tenured fugitives on the FBI's "Ten Most Wanted Fugitives" list, appearing there from 1981 to 2007. Authorities believe Webb shot and killed Saxonburg police Chief Gregory Adams in December 1980 after Adams pulled him over for running a stop sign.

An FBI Wanted poster for Donald Eugene Webb is pictured in this undated handout photo obtained on July 14, 2017. Handout / FBI via Reuters

Webb, then 49, was a jewelry thief from Massachusetts with connections to the New England mob. Police believe he was in Saxonburg, outside Pittsburgh, to case a jewelry store he planned to rob when Adams stopped his car.

Webb disappeared after the killing, but his car was found two weeks later in a parking lot in Warwick, Rhode Island. Within weeks of the killing, a federal arrest warrant was issued for Webb after he was charged with unlawful flight to avoid prosecution and charged in Pennsylvania with first-degree murder.

Police were led to Webb's body Thursday by his ex-wife, Lillian, who showed them where he was buried in her back yard in Dartmouth, Massachusetts. Prosecutors in both Massachusetts and Pennsylvania confirmed to The Associated Press on Friday that authorities have agreed not to prosecute Lillian Webb in the investigation.

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The FBI said investigators believe Webb died about 17 years ago. Gregg Miliote, a spokesman for the Bristol County District Attorney's Office in Massachusetts said Webb's cause of death has not yet been determined, but it "does not appear his death was the result of a violent act."

The police chief's widow, Mary Ann Jones, said she is livid that Lillian Webb kept her ex-husband's whereabouts hidden for years, as Jones and her two sons struggled with their loss and the thought that the killer was still at large.

"I guess I'm angry at her at this point because she could do that to my family — hide him for years and then bury him so we never know," Jones said. "Why hide him? Why not allow us closure?"

Authorities carry lighting equipment to the backyard of the home of Lillian Webb, wife of fugitive Donald Eugene Webb on July 13, 2017 in Dartmouth, Massachusetts. Mike Valeri / Standard Times via AP

Lillian Webb could not be reached for comment Friday. A message was left at her home.

Adams was 31 when he was killed, leaving his wife to raise two young sons. She eventually remarried.

Last month, Jones' lawyer, Thomas King III, filed a notice in court saying Jones planned to sue Lillian Webb and her adult son for civil conspiracy claims after FBI agents said Webb may have hidden out in a secret room in Lillian Webb's home during short stints in the 1990s. A cane was found in the room.

King said Friday that Jones agreed to drop her claims after Lillian Webb agreed to tell authorities where her ex-husband was buried.

Joseph Beachem, the current police chief of Saxonburg, praised the FBI and police in both states for never giving up on finding Webb.

"The biggest question in the history of Saxonburg has been answered," Beachem said. "Our thoughts are with the family and we hope this eases their minds, if even only slightly. While the hurt will continue, at least doubt about what happened that day has been eliminated."

Authorities stand outside the home of Lillian Webb, wife of fugitive Donald Eugene Webb on July 13, 2017 in Dartmouth, Massachusetts. Mike Valeri / Standard Times via AP

State police detectives assigned to Massachusetts Attorney General Maura Healey's office obtained a search warrant for Lillian Webb's property as part of a separate investigation into an illegal gambling operation that led to the discovery of Webb's body. The application for the search warrant said police were looking for Webb's body and evidence of him living in the house before his death.

The FBI offered a $100,000 reward for information leading to Webb or his remains, but said Friday that the reward will not be paid because Webb's remains were found as part of the investigation.