I find it interesting the newspaper took the letter to the police and obviously made the editorial decision not to publish it at this time.
Yes, it is interesting but in my experience as a reporter/editor, just where would you publish this letter - certainly not in the "Letters to the Editor."
Also, if this letter's contents deals with something directly connected to the case, rumor or not, it is potential evidence. Therefore, it should go directly to the cops.
I believe since the letter has no identification as to who wrote it, it would be difficult to authenticate and the paper's policy as to printing the truth would come into question.
Yes, the paper could write "about" the letter and the fact it was received but not print the contents until it is released by law enforcement.
Newspapers, believe it not, and I think you know this awakewriter, receive mysterious messages (notes, letter, phone calls) all the time. But until they are checked out and confirmed, they rarely make into print.
Just using my background to provide this post.