Could it be?

A letter, sent to the San Francisco Police Department in 2013, could prove that the only three prisoners to never return to the apparently impenetrable Alcatraz might have made it after all.

The men broke out on June 11, 1962, after “squeezing through the vents in their cells,” reports TIME:

They had prepared for months, stockpiling necessities to survive their escape from the island in the Pacific Ocean — including a raft made from 50 raincoats, DIY life vests, and paddles.

Since their escape, authorities have never known for sure whether the three men survived, and many assumed they died in the freezing water.

However, the letter below changes all that.

In it, John Anglin allegedly explains that his fellow escapees, brother Clarence Anglin and Frank Morris, have since died: Morris in 2008, Anglin three years later:

“I’m 83 years old and in bad shape,” he writes. “I have cancer. Yes we all made it that night but barely!

“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. This is no joke…”

The U.S. Marshals explained that an FBI lab checked the handwriting and tested for fingerprints and DNA, but the results were inconclusive:

The prison mugshots of the bank robbers, from left to right: Frank Lee Morris, Clarence Anglin and John Anglin:

If the letter proves legitimate, they will be the only three prisoners to have successfully escaped the federal penitentiary:

Of the 36 inmates who staged 14 escape attempts over the 29 years that Alcatraz served as a federal penitentiary, 23 were recaptured, six were shot and killed, two drowned, and five (including Morris and the Anglins) are listed as missing and presumed drowned.

Badass.

[source:time]