PHILADELPHIA -- The FBI kept a thick file on Penn State football coach Joe Paterno, but it mostly involves threatening letters sent to him and his staff years ago, and there's no mention of his former assistant Jerry Sandusky, who was convicted this year of molesting boys.

Paterno's 868-page file shows he received a series of threatening letters sent in the late 1970s and early '80s from someone who signed them A Bitter Father. The author blames Paterno for family problems that apparently surfaced after his son left the university's heralded football program prematurely.

"I feel you are responsible for me loosing (sic) my son," A Bitter Father writes. "He went to Penn State because of you in the first place. He feels he got a bum deal and I agree. He lost interest in everything and went from bad to worse."

Another anonymous letter, to an assistant coach, suggests Paterno was responsible for the assistant's "tragic accident." The file doesn't say what the accident was.

The FBI posted the late coach's file online Wednesday in response to Freedom of Information Act requests from media outlets. The Washington Times first reported on the contents, which also had been mailed to media outlets a day earlier.

Paterno died in January at age 85, two months after losing his job over the Sandusky sexual-abuse scandal.

An FBI memo dated Dec. 16, 1977, said Paterno found the letters troubling.

The FBI withheld 44 pages of Paterno's file, citing privacy issues and the protection of a confidential source.