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.
The FBI spent several years investigating the written threats sent to Paterno, his staff and even a Penn State television commentator, following leads that took agents to a Roman Catholic church and a shipbuilding company in the Pittsburgh area. The leads apparently went nowhere.
Additionally, Penn State basketball coach Dick Harter received a threatening letter in 1980, the file shows.
A Bitter Father later apologized to Paterno, saying he had spoken to his priest and realized he shouldn't blame others for his troubles. But the letters seem to have continued.
Sandusky, Paterno's longtime defensive coordinator, was convicted in June of sexually abusing 10 boys, some on campus. He awaits sentencing and maintains he's innocent.
Former FBI Director Louis Freeh led a recent Penn State internal investigation into the Sandusky matter, faulting Paterno and other university leaders for putting the university's reputation and football program over the safety of children.
Paterno's family strongly denied he protected Sandusky for fear of bad publicity.