A North St. Paul woman finally knows what happened to her younger brother, who was just 16 when he went missing more than 40 years ago.

James "Jimmie" Byron Haakenson was one of the 33 men murdered by serial killer John Wayne Gacy in the 1970s.

"He had so much life ahead," said his older sister, Lorie Sisterman, of North St. Paul. "But he didn't get to do that — have fun, get married — because of this awful man. It's so sad."

The Cook County Sheriff's Office in Illinois announced Wednesday that Haakenson has been identified as one of Gacy's victims — one of seven remaining who had not yet been identified.

Haakenson, who left his St. Paul home in the summer of 1976, called his mother on Aug. 5, 1976, telling her he was in Chicago. He was never heard from or seen again, Cook County Sheriff Thomas J. Dart said Wednesday.

Gacy was convicted in the killings of 33 young men and boys, most found buried in the crawl space beneath his ranch-style home on the northwest edge of Chicago. It was one of the nation's worst serial killing cases. He was executed in 1994.

His victims included male prostitutes, street kids he picked up for sex and youths he hired in his remodeling business.

The killings spanned more than five years, but Gacy wasn't arrested until he was suspected in the death of a teen to whom he had offered a $5-an-hour construction job.

The bodies of 27 victims were recovered beneath Gacy's house beginning in December 1978 with the help of a hand-scrawled map he drew for police. Two other bodies were found elsewhere on his property, and four were pulled from the nearby Des Plaines River.

In 2011, Dart reopened the investigation to identify eight remaining victims. Investigators exhumed the remains and made a public plea to families of young men who went missing in the 1970s to submit DNA samples to be used to seek matches with victims.

Weeks later, investigators identified "Victim 19" as William Bundy, 19, who grew up in Chicago and was last seen October 1976 as he headed to a party.

This week, investigators identified "Victim 24" as Haakenson.

His remains were found in the same grave with two other men, one of whom was identified at the time and another, known as "Victim 26," who remains unidentified. Investigators believe Gacy killed the three men near the same time based on when they were last seen or heard from and their positions in the crawl space.

Haakenson's family filed a missing-person report with the St. Paul Police Department on Sept. 2, 1976 — four weeks after the teen last talked to his mother.

In December 1978, Gacy confessed to police that he had killed 25 to 30 men. Weeks later, Haakenson's mother, who has since died, wanted to know if her son was among the victims. At her urging, St. Paul police sent a letter dated Jan. 3, 1979, to the Des Plaines Police Department, requesting the Illinois investigators check into that possibility.

Without dental records, there was no way to connect Haakenson to any of the remains.

Years passed and the family accepted that Jimmie, an exuberant kid with a big smile, was gone.

"We had to live life," said Sisterman, 61. "We got married. We had kids. We lived life, but always wondering 'Where is Jimmie? Where could he have gone? Why doesn't he call?"

Nearly four decades after Gacy's confession, DNA from Sisterman and her brother led to his identification.

A nephew of Haakenson wondered what became of his uncle who'd gone missing years ago. He urged his father and aunt — Haakenson's brother and sister — to submit DNA samples this year.

There was an immediate hit, Dart said. There was a "strong genetic association with Victim 24." Investigators confirmed it was Haakenson after combing through his case file and other documents.

An Illinois investigator came to Minnesota on Monday to deliver the news to Haakenson's family.

"We no longer have to wonder where Jimmie is," his sister said.

Haakenson is the second Minnesotan killed by Gacy. The body of Russell L. Nelson, 21, of Cloquet, was identified during the initial investigation. Nelson, who majored in architecture at the University of Minnesota, was traveling to Florida to look at buildings in October 1977, stopping in Chicago along the way. He was last seen leaving a disco.

The Cook County sheriff said the push to identify the last six unidentified remains continues. Families of missing men who may have been killed by Gacy can go to the sheriff's website for additional information.

The Associated Press contributed to this report.