The cold case abduction and murder of a 5-year-old Montana girl has been linked through DNA to a man authorities said was passing through town at the time. 

The 1974 case of Siobhan McGuinness haunted detectives and the Missoula community for decades, according to KECI-TV.

Missoula police said Monday that Richard William Davis killed her. He was 70 when he died in Arkansas in 2012.

Siobhan McGuinness was raped and murder after being abducted in Missoula, Montana, in February 1974. (Missoula Police Department)

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Crime scene DNA uploaded to a public genealogy website led to Davis’ identification as the killer. The same genetic genealogy technique has been used to solve other cold-case rapes and murders, including that of the Golden Gate Killer.

“It really means the world. My dad never thought that he would see this happen in his lifetime,” Siobhan’s half-sister Oona McGuinness told the station. “It's a big deal. It's a really big deal for us, and it's a huge deal for the Missoula community. This affected almost everybody that lived there at that time and probably still some today.”

Photos show Richard William Davis in old age and in 1973.  (Missoula Police Department)

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Siobhan was last seen leaving a neighbor’s house in February 1974. Two days later her body was found 10 miles away in a culvert near I-90 in Turah. She had been beaten, stabbed and raped.

Missoula Police Chief Jaeson White said Davis was traveling through the Missoula area when Siobhan disappeared, KECI reported.

“I have always known deep inside that it was a stranger,” Siobhan’s father, Steve McGuinness, 79, told Fox affiliate KTMF-TV, which examined the case a year ago. “Someone who was here for a very brief period of time. On the move. It's like the perfect storm. It was just a couple of blocks. Yep. Couldn't have been more three. It was dinner time in February. It was dim. Twilight. In the winter, windows are closed. You don’t hear what's going on outside. It was like the perfect situation for that to happen.”

The FBI said Monday Davis is also linked to the 1973 attempted abduction of an 8-year-old girl in the upstate New York town of Bath.

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Davis’ obituary posted online described him as a loving husband, father and grandfather. It also said he was a born again Christian “who believed in the word of faith and he was ready to be with Jesus.”