Okay, let's have a go.

Let's find out what we can about the carrier:
[link to en.wikipedia.org]

"According to the FBI, McCormick was 41 when he died. He was a high school dropout, but was able to read and write and was said to be “street smart.” According to members of his family, McCormick had used such encrypted notes since he was a boy, but apparently no one in his family knows how to decipher the codes. Investigators believe the notes in McCormick’s pockets were written up to three days before his death."



Let's see some other codes he carried. even if unsolved, they would give a glimpse into his life.

Like I said, IMO being "street smart" would indicate a nefarious lifestyle. I would bet that his codes would have to be brute-force attacked and with a little luck you may be able to stumble upon the one-time-pad he used.

Find out more about the man and what he did in his life and you may have a jump point.