ADRIAN, MI - Using DNA and with advances in technology, authorities have identified remains buried in a Georgia "pauper's grave" as those of a 15-year-old Addison High School student missing for nearly 40 years.

Andrew Greer ran away from home Feb. 12, 1979. Unbeknownst to police and his family in Michigan, indications are he died two days later, when he was hit by a semitrailer while hitch-hiking down I-75 near Macon in central Georgia, about 800 miles south of Addison, according to a Tuesday statement distributed by Michigan State Police.

It was not until December that police linked the "John Doe" killed in the crash and the boy in Addison.

"The thing is, you want to feel good about it," state police Detective 1st Lt. Thomas DeClercq said Tuesday. "It is a lot more bitter than sweet. It is sad.

"A young boy lost his life, you know, running away."

Decades ago, Greer's mother reported he disappeared from their home on Burton Road in Rollins Township, north of Clayton, and he was last seen on U.S. 127 in Addison, according to Greer's profile on NamUs, a national information clearinghouse and resource center for missing, unidentified and unclaimed people. The only confirmed final sighting was at the high school. State police investigated, but the case went cold.

The file never really was closed. The Lenawee County Sheriff's Office re-opened the inquiry in 2000 and the state police again began an investigation in 2014, according to the statement.

Late last year, a retired sheriff's deputy in Bibb County, Ga. connected the events, state police reported. According to the Daily Telegram, investigators in Georgia came across a story about Greer published in the Adrian newspaper, called upon by a half brother to try to bring attention to the case.

DeClercq, of the Lansing-based First District Special Investigation Section, said the deputy had kept the case in mind all these years and learned of Greer, with a disappearance date so close to the Georgia fatality.

"This is just one of those cold cases, a 15-year-old boy gone missing. People are going to keep looking at that," DeClercq said.

The deputy contacted the state police, and a Michigan detective traveled south in April to exhume the body, with help from the Bibb County Sheriff's Office, the Macon district attorney's office and the National Center for Missing and Exploited Children.

Remains were additionally tested, and the Georgia Bureau of Investigation sent a DNA sample to the Center for Human Identification at the University of North Texas. Results led police to conclude they belong to Greer. It is 1.9 trillion times more likely the "John Doe" and Greer DNA are the same, they showed, according to the statement.

DeClercq said state police had collected familial DNA from Greer's mother's side.

Until now, the identity of the body had been a mystery in Georgia. In 1979, long before computer databases tracked the missing, no information surfaced in Michigan about the teen crash victim and no one in Georgia claimed the body, so it was buried, the Telegram reported.

"The media wasn't what it is now. They didn't have the social media and news..., weren't able to put two and two together," DeClercq said.

Arrangements are now being made to bring Greer's body back to Michigan, according to state police.