The FBI investigated a series of threatening letters sent to Pistons coach Chuck Daly at the height of his success during the "Bad Boys" championship era.

The 67 pages, obtained by the Associated Press, detail how federal agents in Detroit ordered fingerprint, handwriting and even psycholinguistic analyzes as part of an effort to determine who sent the letters.

One letter, mailed from Cleveland and postmarked April 24, 1989, arrived about two months after Cavaliers guard Mark Price suffered a concussion following a Rick Mahorn elbow.

"God made me realize that YOU, not Laimbeer, Mahorn or any of the others are the one possessed by [Satan]," the author wrote in the one-page handwritten letter addressed to "Mr. Chuck Daly."