Alcatraz escapee alive? Letter-writer claims to be one of 3 inmates who swam for freedom in 1962

"My name is John Anglin," the letter begins, according to the CBS affiliate. "I escape (sic) from Alcatraz in June 1962 with my brother Clarence and Frank Morris. I'm 83 years old and in bad shape. I have cancer. Yes we all made it that night but barely!"

The men, all serving time for bank robbery, were discovered to be missing from their cells during a morning bed check on June 12, 1962. According to FBI documents, the men left on their pillows dummy heads made of plaster, flesh-toned paint and human hair that fooled guards long enough for the men to make their daring overnight escape.

All that was ever found in the bay was a packet of letters belonging to one inmate, paddle-like pieces of wood and bits of rubber inner tube, the FBI reported. A homemade life jacket also washed up on a nearby beach.

The letter-writer, who sent his story to San Francisco police five years ago, claimed that he was the only escapee to still be living, CBS San Francisco said. He claimed that Morris died in 2008 and that Clarence Anglin died in 2011.

The man offered to turn himself in.

“If you announce on TV that I will be promised to first go to jail for no more than a year and get medical attention, I will write back to let you know exactly where I am,” the man wrote. “This is no joke.”

Officials with the U.S. Marshals Office, the sole agency still investigating the escape, told CBS San Francisco that FBI lab analysts examined the letter for fingerprints and DNA and that handwriting experts looked at the writing. The results were inconclusive.

The letter-writer claimed that he lived in Seattle for several years after escaping the prison. He also mentioned North Dakota and Southern California as places he called home.

U.S. Marshals Office officials refuted the authenticity of the letter in a written statement. As proof, they pointed to the fact that none of the three men ran afoul of law enforcement in the years after the escape.

"There is absolutely no reason to believe that any of them would have changed their lifestyle and become completely law-abiding citizens after this escape," the statement read.

John Cantwell, a ranger with the National Park Service, which now runs Alcatraz as a museum, also told the news station that he did not believe the men survived the escape.

"The Federal Bureau of Prisons say that they drowned once they got off of Alcatraz and their bodies were swept out to the Pacific Ocean -- end of story," Cantwell said.

Over Alcatraz's 29-year lifespan as a federal prison, 36 men tried to gain their freedom in 14 separate escape attempts, according to the FBI. All were either caught, killed during their escape or presumed to have drowned during the swim across the bay.

The most notorious of those presumed dead are the Anglin brothers and Morris.

The three men spent several months hatching their plan, which included using crude tools, including a homemade drill made from the motor of a broken vacuum cleaner, to widen the air vents in their cells. They used the widened vents to climb into an unguarded utility corridor above their cell block, where they set up a secret workshop in which they created what they would need to get off the island.

Their handcrafted items included homemade life vests and a rubber raft, crafted from more than 50 raincoats they stole, the FBI said. They also made paddles and used a converted musical instrument to inflate the raft.

On the night of the escape, the men used air shafts and a ventilator to the roof to leave the prison, the FBI said. From the roof, they shimmied to the ground on the bakery's smokestack and launched their raft from the northeast shore of the island.

Although investigators believe the men died during their escape attempt, no sign of the men was ever found. In the more than five decades since they vanished, there have been multiple theories regarding their fate.

The letter was just one piece of alleged evidence to turn up in recent years. The History Channel in 2015 aired a special including a photo that purportedly showed the Anglin brothers together in Brazil 13 years after their escape.

If alive today, John Anglin would be 86 years old, and his brother, 87. Morris would be 90 years old.

Besides the escapees, Alcatraz was once home to some of the most notorious criminals in American history. Its one-time inhabitants include gangsters Al Capone and George “Machine Gun” Kelly and the “Birdman of Alcatraz,” Robert Franklin Stroud.

The prison was shuttered in 1963.