BOSTON (Reuters) - Former New England Patriots football star Aaron Hernandez had been upbeat and appeared increasingly spiritual to his fellow prison inmates in the days before he hanged himself in his cell, according to court documents released on Friday.

The documents, which include the first published excerpt of one of the notes that Hernandez left behind in his cell, are based on interviews with fellow inmates at the Massachusetts prison where he had been serving a life sentence for murdering an acquaintance.

Hernandez's suicide last month stunned his loved ones, according to family attorneys, because it came just days after he been found not guilty of a 2012 double murder.

The documents include a Department of Corrections Report that noted that one inmate said conversations with the 27-year-old former athlete had become increasingly religious in tone in the days leading up to his death.

"This inmate stated that Hernandez came to his door before lock in and stated, 'remember when you die your soul gets reincarnated,'" the report said. It quoted another person, who claimed to be one of Hernandez's best friends, who said Hernandez had discussed hopes of returning to professional football.

Hernandez's body was found with the words "John 3:16" written on his forehead in ink and on the wall of his cell in blood, according to a state police report released on Thursday. The words were an apparent references to the Bible verse that begins "For God so loved the world, that he gave his only Son."

The court papers also included an excerpt of one of three handwritten notes found in Hernandez's cell along with his body. Addressed to "Shay," his fiancée Shayanna Jenkins Hernandez, it reads in part, "tell my story fully but never think anything besides how much I love you."

The attorneys who successfully defended Hernandez in the double-murder trial released a statement late Thursday criticizing state officials for having leaked some details of the report to local media ahead of its release.

"We intend to fully, completely and impartially review all of the evidence in this matter," Hernandez's attorneys said in the statement. "We will not speculate as to the conclusions of our investigation."

(Reporting by Scott Malone; Editing by Mary Milliken)