A group of documentary filmmakers who also work as cold-case investigators believe they’ve decoded a 1972 message purportedly from D.B. Cooper, and they say it contains a confession from Robert Rackstraw, the New York Daily News reports.

Rackstraw is a Vietnam veteran who has long been considered by some to be the likely culprit in the hijacking of a Seattle-bound plane. Months after the mysterious hijacking and D.B. Cooper’s parachute escape, The Portland Oregonian newspaper reportedly received a letter that the investigators say they decoded. They believe their work proves that he is indeed the same person as the fictitious D.B. Cooper, according to New York Daily News.

Rackstraw, a 74-year-old San Diego resident, is reportedly alive and well.

After hijacking the plane in 1971, the man who identified himself as Dan Cooper parachuted out of the aircraft with $200,000 in tow, and was never heard from again.

Wearing a suit and tie, the suspect reportedly told a flight attendant that his briefcase contained a bomb and handed her a note demanded ransom money. In compliance, pilot landed the plane and Cooper let the 36 passengers go in exchange for $200,000 cash, which was paid in $20 bills. He also demanded parachutes before ordering the plane to fly to Mexico. Then, the hijacker jumped via the parachute near the Washington-Oregon border.

The letter claimed to be written by the suspect taunted investigators.

“This letter is too [sic] let you know I am not dead but really alive and just back from the Bahamas, so your silly troopers up there can stop looking for me,” the letter to The Portland Oregonian reads.

“That is just how dumb this government is. I like your articles about me but you can stop them now. D.B. Cooper is not real. I want out of the system and saw a way through good ole Unk,” the letter reads, with “Unk” referring to Uncle Sam.

“Now it is Uncle’s turn to weep and pay one of it’s [sic] own some cash for a change. (And please tell the lackey cops D.B. Cooper is not my real name).”

The private investigative team on the case was led by documentary filmmaker Thomas Colbert, who told New York Daily News that he obtained the letter after successfully suing the FBI for the files. Colbert said he observed that the letter appeared to be eerily similar to another letter…and he ultimately called a code breaker, Rick Sherwood, to try and get to the bottom of the case.

“Nobody even knew about this letter,” Colbert told the Daily News. “When I got it, I noticed it was typed just like [another Cooper letter], so I called a code breaker and showed it to him. He said, ‘Tom, you’re not going to believe it, but the confession is here.”

Sherwood, a former Army Security Agency member, revealed to New York Daily News that he was able to uncover similarities with the words “D.B. Cooper is not real,” “Unk” or “Uncle,” “the system,” and “lackey cops.” He said that he decoded “through good ole Unk” to translate to “by skyjacking a jet plane” by using a system of both numbers and letters.

“And please tell the lackey cops,” translated to “I am 1st LT Robert Rackstraw,” Colbert said, according to the newspaper.

Sherwood claims that earlier letters he deciphered from Cooper made him familiar with the man’s writing style.

“I read it two or three times and said, ‘This is Rackstraw, this is what he does,’” Sherwood told the media outlet. “I noticed he kept on repeating words in his sentences and thought he had a code in there somewhere.”

“He was taunting like he normally does and I thought his name was going to be in it and sure enough the numbers added up perfectly,” Colbert said, adding that the entire decoding process took him a mere couple of weeks.

Rackstraw was previously investigated but later cleared by officials. However, some still believe he is the elusive hijacker.

“Rackstraw is a narcissistic sociopath who never thought he would be caught,” Colbert told the Daily News.

“He was trying to prove that he was smarter than anyone else. But he couldn’t fight 1500 years of brainpower on our team. We beat him. I didn’t expect it, but it’s the icing.”