Aaron Hernandez, who played for the New England Patriots, was serving a life sentence for the 2013 murder of a man who dated his fiancée's sister.
According to police, Hernandez hanged himself in his cell on 29 April, which is five days after he was acquitted in the 2012 fatal shootings of two men in a car.
Investigators said they also found a fresh cut and blood on Hernandez's fingers, as well as a Bible opened to John 3:16 with the verse marked in blood.
Three handwritten notes were found next to the Bible.
The report stated there also appeared to be a large circular blood mark on each of his feet.
State police said a review of video surveillance showed Hernandez was on the phone just before being locked in his cell. Police said they listened to the last five phone calls Hernandez made.
"Hernandez does not make any apparent indication of an intent to harm himself during any of the phone calls," the report stated.
Hernandez's lead attorney in his double murder trial has pledged to do an independent investigation into his death.
