CHICAGO — After running away from his Minnesota home in 1976, 16-year-old Jimmy Haakenson called his mother, told her he was in Chicago, then disappeared forever.

More than 40 years later, a detective from Illinois arrived at the family’s home to tell Haakenson’s relatives that at some point after hanging up the phone, the teenager crossed paths with serial killer John Wayne Gacy. Haakenson’s body, it turns out, was among dozens found in a crawl space of Gacy’s Chicago-area home in 1978. But the remains were only recently identified thanks to DNA technology that wasn’t available then, the Cook County Sheriff’s Department announced Wednesday.

Gacy was convicted of killing 33 young men and was executed in 1994. But the revelation about Haakenson is the latest turn in a yearslong effort to solve the remaining mystery surrounding Gacy’s case: Who were the eight victims authorities hadn’t been able to identify?

James “Jimmy” Byron Haakenson’s body is only the second person that authorities have identified since Sheriff Tom Dart in 2011 ordered the remains of the eight victims exhumed and asked families of young men who went missing in the 1970s to provide DNA samples. The first was William Bundy, a 19-year-old construction worker from Chicago whose remains were identified weeks after the exhumations.

Haakenson’s family in Minnesota plans to come to Chicago to mark his grave.

“One of the worst people in the world that walked the earth murdered my brother,” his sister, Lori Sisterman, who lives in North St. Paul, said Wednesday. “You hope for something different,” but she went on to add, “I’m so glad to know where my brother is.”

Gacy is remembered as one of history’s most bizarre killers, largely because of his work as an amateur clown. The Chicago-area building contractor lured young men to his home by impersonating a police officer or promising them construction work. There, he stabbed one and strangled the others. Most of the victims were buried under his home, but others were dumped in a river.

Illinois investigators long referred to Haakenson as simply “Victim #24.”

Haakenson came to Chicago hoping to strike out on his own in a city far bigger than the community of St. Paul where he lived, Dart said. According to Sisterman, the teenager had finally made good on his angry vows to his mother that he was going to run away.

He was a boy, said Sisterman, who kept “trying to find himself.”

After bodies were found in Gacy’s home, Haakenson’s mother was suspicious enough that her son was among the victims that she came to Chicago to talk to investigators. But she left without any answers because there was no way to identify the skeletal remains without dental records, Dart said. The mother died a couple of decades later.

Dart said a nephew of Haakenson became curious about the uncle he never knew and earlier this year went online to see if he could learn anything. That’s when he discovered Dart’s efforts to identify the remains of the eight young men.

Dart said the nephew went to his father, Haakenson’s brother, and his aunt, Lori Sisterman, and persuaded them to submit the samples for testing.

“We got an immediate hit,” Dart said.

Authorities believe the teen was killed in August 1976, in part because of where he was found in Gacy’s house. Because Gacy was killing so many young men, his crawl space was filling up, forcing him to stack the bodies. Haakenson’s body was directly underneath Rick Johnston, who was last seen at a concert in Chicago on Aug. 6, 1976, and was on top of a still unidentified young man known as “Victim #26.”

Over the course of the investigation, the Cook County Sheriff’s Department has solved a number of cold cases. According to the department, investigators have located five missing persons who were alive and two missing persons who had died elsewhere in the country. For example, in 2013, Dart announced that one person who submitted DNA had allowed investigators to identify remains found in a wooded area in New Jersey as a teenager who ran away from a nearby orphanage in 1972.

Cook County Sheriff Tom Dart, left, speaks at a news conference in Chicago, Wednesday, July 19, 2017, where he announced the identity of James Byron Haakenson, of Minnesota, as one of the victims of serial killer John Wayne Gacy. The teenager had left his home in 1976 and was last heard from in August of that year when he called his mother and told her he was in Chicago. (AP Photo/G-Jun Yam)