Daniel Noe. Image Credit: Cook County Sheriff's Office

CHICAGO - In the fall of 1978, 21-year old Daniel Noe was heading home to Chicago from a stint working out west when he mysteriously vanished. For the past three decades, his parents have wondered what happened to their missing son and now, thanks to a search to identify victims of serial killer John Wayne Gacy, they have an answer.

Noe, as it turned out, was not one of Gacy's victims, but the ongoing probe into the serial killer's murders helped authorities crack Noe's cold case.

Still wondering what happened to his brother, Michael Noe contacted the Cook County Sheriff Tom Dart after he heard Dart's office was attempting to identify Gacy's victims.

"He was going through an area where Gacy had been known to try to grab people," Dart said. "It fit the timeframe."

So authorities went to Noe's parents, Raymond and Phyllis, to collect DNA samples to see if they turned up a match. The samples did not match any of Gacy's victims, but they did match some remains that were found on a Utah mountainside in 2010, news that Dart broke to Noe's family this week.

"Last Sunday he called and wanted to come back and see us on Monday, and they had an unidentified body in Utah and it matched it," Phyllis Noe, now 87, told ABC News in a phone interview.

While the definitive news that their son had died hurt, the fact that the family now had "a sense of closure" was a relief, she said.

"It's been a long time, and it's really good to know that it's over with," she said.

That was the same sentiment expressed by her husband, Raymond Noe, who lives with her outside Peoria, Ill..

"The main shock was over 30 years ago, but it's still a shock to us. It was kind of good news, kind of bad," he said. "Good because it will bring closure, but bad because they didn't find him alive. He's been on that mountain all those years."

After spending some time working in Oregon and Washington state, Daniel Noe in 1978 decided to hitch hike home to Chicago, where he was studying at Northwestern University. On Sept. 30, Noe phoned his parents and told them about his plans.

"He called home and said he was coming back to Chicago to pick up his last credit to graduate," Raymond Noe said. "He wouldn't be able to get a good job without it, so he said he'd hitch hike back and see us in two weeks. That was the last we heard of him."

On his way back to Illinois, Noe stopped off in Utah.

"It appears that he decided, as a diversion, to go hiking there," Dart said. "A friend of his dropped him off. The two of them were avid hikers and apparently, at some point, with no evidence of any foul play, he died on the side of the mountain back in 1978."

As the weeks went by, Noe's parents grew increasingly worried about their son's whereabouts, finally going to the authorities around Thanksgiving.

"We waited to give him enough time to check in, but he never did," his father said.

More than three decades passed until Noe's brother heard about the probe to identify Gacy's victims. In 2010, Dart called for families of young white men who disappeared in the 1970s to contact authorities as part of the sheriff's attempt to identify people who may have fallen prey to the serial killer and rapist, who murdered at least 33 boys from 1972 to 1978. The DNA from Noe's parents did not turn up a match to any of Gacy's victims, but it did signal a match in the national database.

"We never expected it would work, but evidently it did," Raymond Noe said.

And now, 34 years after their son vanished, the Noe family at last knows what happened to him. A funeral is scheduled for Tuesday morning near the couple's hometown of Washington, Ill.

"The strangeness of where everything ended up as far as where their son, you know, passed away, that was a little bit different, but they were completely reserved and there was almost a sense of serenity," Dart said about the moment he broke the news to Noe's parents.

"To be able to say that he died doing something that was, you know, kind of nice like mountain hiking was very good for the family," said Detective James Moran.