The old man died as he lived — obscure and alone. On July 24, 2002, the 76-year-old snapped the locks on all the windows and doors in his apartment in a Cleveland suburb. He marked the date on his calendar and shut off the air conditioning. Then, as law enforcement officials later recounted, he walked into his bathroom, placed a gun under the roof of his mouth, and pulled the trigger.

It would take police nearly a week to discover the remains of the man known as Joseph Newton Chandler III. The summer heat pressing in on the unit turned the apartment into an oven. The body was badly decomposed. Authorities could not even lift fingerprints off the corpse.

Chandler, an electrical engineer, left behind few clues about his life. He was a loner, his co-workers told police, extremely smart but bizarre. He would sit listening to radio static for hours, the Morning Journal reported. Chandler once drove from Ohio to Maine to visit an L.L. Bean store, then immediately turned around and returned when he couldn’t find a parking space in the lot, the Journal said. It was not out of the ordinary for Chandler to vanish from town for days and weeks. “They are getting close,” was all he would cryptically tell people once he arrived home.

The dead man had $82,000 (U.S.) in a bank account. Police searched for a next of kin. On a rental agreement, Chandler listed a sister in Columbus. But the address — 1823 Center Street — only led to a vacant lot. Authorities dug deeper. As U.S. Marshal Pete Elliott told reporters at a news conference this week, that was when “a typical suicide” turned into “one of northeast Ohio’s biggest mysteries.”

Using the deceased’s name, birth date, and Social Security number, Ohio police discovered records for Joseph Newton Chandler III.

But Joseph Newton Chandler III had been killed with his parents in a Texas car crash when he was 8-years-old in 1945.

If the real Chandler had died a half-century earlier, who was the dead man in Ohio?

For the last 16 years, speculation about the dead man’s identity has stumped law enforcement. Wild theories have wrapped around the case — could he have been the Zodiac Killer? Mysterious hijacker D.B. Cooper? Why was he hiding behind the stolen identity?

After years of work, including groundbreaking DNA testing and genealogical research, authorities revealed on Thursday the man living for decades as Chandler was Robert Ivan Nichols, an Indiana native and decorated World War II veteran who slipped out of his given identity in the 1960s. But law enforcement officials admit they still don’t understand Nichols’ motivation.

“The first part of the mystery is solved,” Elliott told reporters, explaining he hoped information from the public will help cobble together the full answer. “We figured out this part. Let’s figure out the rest of the story.”

The solution to the identity riddle is also a testament to how new science is making it harder for old secrets to remain hidden in the past. As with the Golden State Killer case, Nichols’ secret was uncovered thanks to the same genealogical research used to link long-lost family members, a technology that has armed law enforcement with a critical new tool.

In 2014 the U.S. Marshals Service took over the investigation to run the mystery man against open fugitive cases, Elliott told reporters this week. Although the corpse had been cremated years earlier, Eillott and his team learned the man living as Chandler had had a medical procedure in 2000, and the hospital still had a tissue sample. A local crime lab ran the material through various DNA databases. No matches registered.

Two years later, Elliott asked Colleen Fitzpatrick and Margaret Press, two DNA and genealogical researchers, for help.

“This was the first investigation in Marshall Service history that we utilized forensic genealogy,” Elliott said.

The Eastlake man died in 2002, but authorities have been perplexed by his true identity after learning he stole the identity of a dead 9-year-old boy.

Using the Y chromosome data from the sample, the scientists and a team of volunteers ran the material through the growing public databases of genealogical data from services like Ancestry.com and 23andMe. The searches turned up a probable match to a family line tracing back to an immigrant from 1700s named “Nicholas.”

“We did some genealogy on that, but as you can imagine that decedent has thousands and thousands of descendants, so we really could not see where ‘Mr. X’ fell into that family at all,” Fitzpatrick told reporters this week. “But we can say, assuming he was not adopted or he did not experience an illegitimacy or a name change in his male family, his probable last name was ‘Nicholas’ or a variation.”

The remaining sample proved to be a problem.

Loading... Loading... Loading... Loading... Loading... Loading...

After years, only 7 per cent of the man’s genome remained. Thanks to advanced technology, the researchers were able to still sequence the data and upload the results to “GEDmatch,” a website that allows individuals to post their DNA results for genealogical research. The database provided various matches with the material.

Diving into the family trees, the researchers found a link with a couple named Alpha and Silas Nichols from Indiana. The address from the family was startlingly familiar — 1823 Center Street, the same address the man posing as Chandler had used for his fictitious sister.

“When we compared those two documents, we said, ‘Bingo, we’ve got him,’” Press told reporters.

The couple — long dead — had four sons. Three were no longer living. There were no records for the fourth son, Robert Ivan Nichols, after the mid-1960s.

Last spring, Elliott and another Marshall tracked down Nichols’ son Phillip Nichols to an address in Ohio. The investigators showed him a photograph of the man they were hoping to identify.

“Once I saw the photos, I knew it was him,” the son told reporters.

According to Elliott, Robert Ivan Nichols had served in the U.S. Navy in World War II, suffering serious injuries in the Japanese bombing of the USS Aaron Ward. He returned from combat with a Purple Heart, yet still burned his military uniforms after leaving the service. He was married and had three children, but filed for divorce and left in 1964, only telling his wife she would know why “in due time,” Elliott said.

The last trace of Nichols was a letter he sent to Phillip in 1965, postmarked California, and containing a single penny. The family never heard from him again, eventually filing a missing person’s report later that year. Internal Revenue Service records show Nichols worked under his real name until 1976.

How Nichols learned about the dead 8-year-old is still a mystery, Elliott said. But in 1978, he wrote to the hospital in Buffalo, where Chandler was born. He requested and obtained a copy of the child’s birth certificate. Using the information on the document, he applied for a Social Security card under the boy’s name, and the document was shipped to Rapid Center, South Dakota.

By fall 1978, he was living and working in the Cleveland area under the name Joseph Newton Chandler III.

According to authorities, neither Nichols nor Chandler have criminal records. Elliott, however, said it was clear the lonely man was willing to abandon his life in Cleveland at a moment’s notice. Nichols always kept a packed suitcase in his apartment, the marshal said.

What he may have been running from, however, is still a tangled mystery.

“This has put to rest, at least partially, a mystery within our family,” Nichols’ son Phillip told reporters. “I hold no animosity whatsoever. I always hoped he found a happy life somewhere.”