The letter to his fiancee Shayanna Jenkins-Hernandez was one of three found in the former New England Patriots player's prison cell at the Souza-Baranowski Correctional Center in Shirley, Massachusetts, after he was discovered hanging in the early morning hours of April 19.
Hernandez and Jenkins-Hernandez have a 4-year-old daughter.
In another part of the letter, he wrote in a parenthetical aside "(YOU'RE RICH)."
State prosecutors are hoping to use the letter to argue that Hernandez's murder conviction should not be vacated in the wake of his suicide, as it would "reward the defendant's conscious, deliberate and voluntary act," according to a court filing.
Massachusetts is one of several states that has recognized a legal rule called "abatement," in which courts throw out convictions for defendants who die before their appeal is heard.
Vacating the conviction could complicate legal proceedings for Lloyd's family, who has sued Hernandez for damages in civil court.
Hernandez's attorneys have asked Bristol County Superior Court to vacate the conviction, which is generally automatically granted, legal experts have told CNN.
However, prosecutors filed a motion opposing the abatement. They argued that abatement lacks any solid historical or legal basis, and added that Hernandez's death technically completed his life sentence.
"A defendant, who can cut off his own criminal appeal by suicide and stall civil litigation by a stay of proceedings and then prevent application of collateral estoppel, has the reins of the entire justice system in his own hands," prosecutors wrote.
Why does Hernandez write, "You're rich," in the note? When Aaron Hernandez was arrested for the murder of Odin Lloyd, he was still owed part of a signing bonus and salary worth about $6 million-not $15 million-from the Patriots.
Some legal experts say the family could demand the Patriots to pay up that money.
There would be some legal wrangling and there's an argument to be made, but ultimately it would be up to a judge whether the family gets the remainder of what Hernandez was owed.
Hernandez was serving a life sentence for murder at the Souza-Baranowski Correctional Center. The Worcester County District Attorney's Office and the Massachusetts State Police on Thursday released their report on the investigation into his death, which had been ruled a suicide.
The report shares chilling new details on the circumstances surrounding Hernandez's death.
According to the report, Hernandez was "naked" when he was discovered hanged from a bed sheet tied around the cell's window bars. A postmortem toxicology of the former NFL player's blood came back negative for all substances tested, including synthetic cannabinoids.
Once a star NFL tight end, Hernandez, 27, was acquitted less than a week before his death of killing two men in 2012. He was already serving a life sentence without the possibility of parole for the 2013 killing of semiprofessional football player Odin Lloyd, who was dating the sister of Jenkins-Hernandez.
Investigators determined with a "reasonable degree of certainty" that the letters found in Hernandez's cell were written by him, the report states.
State authorities took custody of the letters before releasing them to Hernandez's family, according to the Worcester County District Attorney's Office.
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