SEATTLE – The “credible suspect” that the FBI is investigating in the D.B. Cooper skyjacking case is a man named Lynn Doyle Cooper, who reportedly died in 1999.

ABC News first revealed the name Wednesday in an interview with Cooper’s niece, Marla Cooper, who said she is cooperating with the FBI.

Steve Dean, the assistant special agent in charge of the criminal division of the Seattle FBI office, confirmed Wednesday that Marla Cooper had contacted the bureau and turned over items to assist in the investigation.

Cooper, citing childhood memories, told ABC News she is convinced her uncle was the man who hijacked a Seattle-bound jet on Thanksgiving Eve 1971 and parachuted over southwest Washington with $200,000.

“I’m certain he was my uncle, Lynn Doyle Cooper, who we called L.D. Cooper,” she told ABC News.

Although some investigators concluded the skyjacker died in the jump, a body was never found in what remains America’s only unsolved hijacking.

The FBI said earlier this week that it was investigating “a promising lead” in the case, but would only identify a possible suspect as a man who died more than 10 years ago.

Cooper, whose hometown wasn’t revealed, told ABC News that she is working on a book about her uncle, but said that wasn’t her primary motivation for coming forward.

Cooper said she was 8 years old at the time of the fabled skyjacking. She said she recalled her uncle and a second uncle planning something suspicious at her grandmother’s house in Sisters, Ore.

“My two uncles, who I only saw at holiday time, were planning something very mischievous,” Cooper told ABC News. “I was watching them using some very expensive walkie-talkies that they had purchased. They left to supposedly go turkey hunting, and Thanksgiving morning I was waiting for them to return.”

After Northwest Orient Flight 305 was hijacked, L.D. Cooper came home claiming to have been in a car accident, Cooper told ABC News.

“My uncle L.D. was wearing a white T-shirt and he was bloody and bruised and a mess, and I was horrified. I began to cry. My other uncle, who was with L.D., said Marla just shut up and go get your dad,” she said.

Cooper said she is now convinced the car accident was a ruse and that her uncle was injured in a parachute jump.

Cooper also told ABC News she remembers a discussion about the money. “I heard my uncle say ‘We did it, our money problems are over, we hijacked an airplane,’” she said.

Cooper says that her two uncles wanted to return to search for the cash, apparently because it was lost in the jump. But her father refused, she told ABC News, probably because the FBI was beginning to search the area where L.D. Cooper was believed to have landed.

Cooper said she never saw her uncle again after that Thanksgiving and was told he died in 1999. She said she believes he lived in the Northwest and had children.

In the ABC News interview, Marla Cooper displayed a 1972 Polaroid picture of her uncle, whom she identified as a Korean War veteran. She said the picture is similar to the composite sketch of the hijacker.

FBI spokesman Fred Gutt said Monday that the bureau’s Seattle office has been investigating for more than a year a lead that has “more credibility and detail” than other tips.

Gutt said the FBI’s vetting of the case warrants further investigation, noting little contradictory information has emerged that would rule out the possible suspect. But he said that doesn’t mean the case is about to be solved.

Gutt said Wednesday that the case is not a high priority, but the new information can’t be ignored.

Cooper told ABC News she contacted the FBI “as soon I was sure that what I was remembering were real memories.”

“There’s a crime that’s taken place that hasn’t been solved, and I’m the only one, as far as I know, who knows what happened,” she said.