Image: Steven Soden

A DNA test used by investigators to identify victims of serial killer John Wayne Gacy has helped solve a 41-year-old New Jersey missing persons case, officials announced Tuesday.

Sixteen-year-old Steven Soden went missing on April 3, 1972, but his remains were not identified until 2012, when authorities matched them with a DNA sample from his sister.

Soden's relatives contacted the Cook County Sheriff's Office in 2011 after hearing about Sheriff Thomas Dart's efforts to identify several of Gacy's victims. They believed Soden may be one of them, officials said.

"We always had hopes that we'd somehow find him alive," Steven's brother, Ron Soden, 73, told NBC 4 New York Tuesday from his home in Tacoma, Wash. "In this day and age, it's so much easier to find someone over the Internet."

The teen, who lived at an orphanage, was last seen alive on April 3, 1972, running away with 12-year-old Donald Caldwell, from the Bass River Camp Grounds in Burlington County, N.J., during a group camping trip, officials said. Neither boy was ever seen again.

Soden may have headed to Chicago, where his biological father lived, his relatives suggested — and there he may have come into contact with Gacy.

Tim Boyle / Des Plaines Police Department vi

This is John Wayne Gacy's police arrest photo from Dec. 21, 1978. Following intensive research, investigation and surveillance, Gacy was arrested by the Des Plaines, Ill., Police Department on Thursday, Dec. 21, 1978.

Gacy killed 33 teenage boys and young men in Chicago from 1972 to 1978. He was executed for his crimes in 1994. Seven of his victims remain unidentified.

At Dart's request, a DNA sample was taken from Soden's sister, but there was no match between her and any of the unidentified Gacy victims.

In December 2012, however, her profile matched that of unidentified human skeletal remains found 13 years earlier in New Jersey.

Over the next few months, the Cook County Sheriff’s Office and New Jersey State Police conducted further investigation and obtained additional DNA samples from Soden's half siblings, including a paternal half sibling, to make an accurate identification.

Genetic testing was performed at the University of North Texas Center for Human Identification.

The remains were discovered in the woods in Burlington County in April 2000 — not far from where Soden was last seen.

New Jersey State Police say they're still searching for Caldwell as well as additional evidence in Soden's death, according to Philadelphia NBC affiliate WCAU. His exact cause of death is still unknown.

"You always hope for the best," Ron Soden told NBC 4 New York. "But when you finally get an answer, a partial answer…" He trailed off.

"It's sad," he continued. "The sense of him being so young, and the way it happened, and where it was. He probably ran away because he thought nobody cared about him. It's just not a good story."

DNA evidence identified Victim No. 19 — labeled as such because his was the 19th body removed from the killer's basement — as William George "Bill" Bundy, 39, Sheriff Tom Dart said Tuesday. The body was found in the crawl space of Gacy's house on Dec. 28, 1978.

Bundy had been reported missing on Oct. 27, 1976, and his family always believed that he might have been a victim of Gacy. But the only identification tool available at the time was dental records, and Bundy's records had been destroyed by his retired dentist.

Bundy's brother, Robert, and sister, Laura, who attended the news conference Tuesday, provided comparison DNA to the sheriff's department, which sent it to the University of North Texas Center for Human Identification.

"Because of all this, Victim Number 19 isn't going to be known as a number anymore," Dart said.

• Read the original story on NBCChicago.com

"Closure is great, but my only wish in this particular case would have been that we could have provided some sort of closure for William's mother and father before they passed away," Dart said. "I do hope and pray that Laura and Robert might find some peace and closure with the news today."

Laura Bundy said she believed from the beginning that her brother was a victim of Gacy, who was a construction contractor. Bundy was also a construction worker, and "he was always all over the city," she said.

"When that happened and I found out that Gacy was a contractor, I just knew it," she said.

Dart announced in October that his office had obtained DNA profiles for all of the notorious serial killer's remaining victims and asked that anyone with missing loved ones to come forward to give DNA samples.

After the request, more than 30 people contacted the sheriff's office in hope of matching names to the remaining eight Gacy victims. Four samples came back from the North Texas institute without matches.

Gacy was convicted of murdering 33 young men and boys, most of whom were found buried in the crawl space of his Norwood Park Township home near O'Hare Airport. The former construction contractor was executed in May of 1994.