Authorities offered few answers after Hernandez was found hanging from a bedsheet Wednesday in his cell in a maximum-security prison in Massachusetts, where he was serving a life sentence for the 2013 slaying of a onetime friend.

BOSTON Aaron Hernandez's death in prison has been ruled a suicide and the former NFL star's brain is being donated to sports concussion researchers, Massachusetts authorities said Thursday.

The declaration by prosecutors, state police and public health officials came after a tumultuous day in which Hernandez's lawyer suggested the state was mishandling the investigation and illegally withholding his brain after releasing the rest of the body to a funeral home.

Authorities said the medical examiner had ruled cause of death was asphyxia by hanging.

"There were no signs of a struggle, and investigators determined that Mr. Hernandez was alone at the time of the hanging," the statement read.

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HERNANDEZ LEFT THREE NOTES IN HIS CELL NEXT TO A BIBLE: TELEGRAM.COM

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Hernandez had been locked into his cell at about 8 p.m. and no one entered the cell until a guard saw him just after 3 a.m. and forced his way in because cardboard had been jammed into the door track to impede entry, authorities said. Hernandez was found hanging from a bedsheet and rushed to a hospital, where he was pronounced dead about an hour later.

Earlier Thursday, Hernandez's lawyer complained that state officials had turned over the 27-year-old's body but not his brain.

Attorney Jose Baez said the family had arranged for researchers at Boston University's Chronic Traumatic Encephalopathy Center to take custody of the brain. The center studies a progressive degenerative brain disease found in some athletes who have experienced repetitive brain trauma. Hernandez's body is at a Boston-area funeral home, but services will likely be held elsewhere for the Connecticut native.

Baez says he's retained Dr. Michael Baden, a former chief medical examiner for New York City, to perform an independent autopsy.

Baden, who didn't immediately comment, has performed autopsies in several high-profile cases, including the death of Michael Brown, a black teen who was shot and killed by a white police officer in Ferguson, Missouri in 2014.

Baez declined to say whether he or the family believed brain damage from Hernandez's playing days led the 27-year-old former New England Patriots player to kill himself.

"We're not suggesting anything," he said. "You go where the evidence takes you. We need to examine every aspect of this case."

It's generally best for researchers to get access to a brain within hours of death to determine the presence of Chronic Traumatic Encephalopathy or other neurodegenerative diseases, said Dr. Lee Goldstein, a CTE researcher at Boston University. Researchers also prefer to receive the entire brain as a small piece may not tell the whole story, he added.

Other questions surrounding Hernandez's death still remain unanswered.

Authorities have still not released the incident report, officers' logs or video footage from the area around Hernandez's cell, despite repeated requests from The Associated Press.

Massachusetts Gov. Charlie Baker said he wasn't drawing any conclusions until the full details of investigation are revealed.

"Any time someone kills themselves in prison something clearly went wrong," he said, adding that he had full confidence in prison officials and was unaware of any staff being reprimanded.