Zodiac Killer Bomb

On July 31, 1969, no one knew of the Zodiac Killer was responsible for at least two unsolved murders in the Vallejo area, until three separate letters, each accompanied by a cipher, were sent to three local newspapers. The combination of the three ciphers consists of 408 characters and is referred to as the "408".  There were 18 characters left at the end of the cipher that has remained unsolved.