The Zodiac Killer is one of the most infamous and recognizable names in the true crime world. Claiming to be responsible for the murders of 37 people (though investigators have only been able to confirm 5), the Zodiac Killer gets his name from letters he signed with a zodiac symbol. Throughout his attacks, he would write letters and send them to the Bay Area press to strike fear and chaos in the community, as well as taunt police. But they weren’t just ordinary letters. They were ciphers, messages written in a secret code.

One of those ciphers has especially puzzled the cryptography community, law enforcement, and true crime fanatics. Until now.

An international team of code-breakers has finally deciphered the 340-character letter that was mailed to the San Francisco Chronicle over 50 years ago. The FBI has verified the breakthrough.

American code-breaker David Oranchak, along with Australian mathematician Sam Blake and Belgian programmer Jarl Van Eycke, was able to translate the grid of 63 unique, mysterious symbols to the following message:

I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO CATCH ME

THAT WASN’T ME ON THE TV SHOW

WHICH BRINGS UP A POINT ABOUT ME

I AM NOT AFRAID OF THE GAS CHAMBER

BECAUSE IT WILL SEND ME TO PARADICE ALL THE SOONER

BECAUSE I NOW HAVE ENOUGH SLAVES TO WORK FOR ME

WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE

SO THEY ARE AFRAID OF DEATH

I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS

LIFE WILL BE AN EASY ONE IN PARADICE DEATH

This particular cryptic message was sent by the Zodiac killer in 1969, after a schoolteacher and his wife cracked the first code. The killer made this one more complex. Even a supercomputer that was specifically designed to think like the killer could not crack it. But the trio of amateurs solved it after a year using Van Eycke’s code-breaking computer program and over 650,000 variations written by Blake.

Oranchak was testing out his different variations by inputting them in the program. He noticed one of them contained phrases such as “hope you are” and “trying to catch me.” So he changed the program’s settings to recall those phrases and solve the rest, which gave clearer lines of text. When he saw the phrase, “that wasn’t me on the TV,” Oranchak said he jumped out of his seat.

For context, two weeks before the killer sent that letter, someone claiming to be him appeared on a morning TV news show saying, “I don’t want to go to the gas chamber.”

Although the case of the Zodiac Killer remains an ongoing investigation, the new discovery could lead to some long awaited answers.

FBI spokeswoman Cameron Rogers Polan said in a statement, “The FBI is aware that a cipher attributed to the Zodiac Killer was recently solved by private citizens. The Zodiac Killer case remains an ongoing investigation for the FBI San Francisco division and our local law enforcement partners.”