Former NFL player Aaron Hernandez was found hanged on Wednesday in the prison where he was serving a life sentence for murder, officials have confirmed.
Baez said the family decided on giving the brain to Boston University to seek signs of chronic traumatic encephalopathy (CTE) - the debilitating brain disease that researchers say is caused in part by concussions while playing American football and other head trauma.
Hernandez family lawyer Jose Baez said earlier Thursday the medical examiner was "illegally" holding the brain after releasing the body to a funeral home.
The Worcester County District Attorney Office has officially ruled Aaron Hernandez's death was a suicide.
Authorities in MA say Aaron Hernandez's brain is being turned over to university researchers now that they've ruled his death in prison a suicide. Hernandez was found hanging from a bedsheet in his prison cell at about 3 a.m. on Wednesday, according to officials.
Baez on Thursday said the family was in mourning, but declined to comment on a range of new reports, including that Hernandez was on the phone with his fiancee, Shayanna Jenkins-Hernandez, hours before he was found hanging in his cell early Wednesday.
Law enforcement sources told ABC News that Hernandez was found with the Bible verse John 3:16 written across his forehead in red marker.
The double murder charges were brought against Hernandez after he had been convicted of the shooting murder of an associate, Odin Lloyd, in 2013, in North Attleborough, Mass., near his home and the Patriots' Gillette Stadium.
"We need to leave no stone unturned, and we need to specifically do everything possible to find out what happened", Baez said Thursday.More news: Hawaii lawmakers criticize Sessions' island judge remarks
Hernandez - who had "God forgives" tattooed on his arm - had not been considered at risk of suicide, Mr Fallon added.
According to NBC News, several football players have been diagnosed with CTE, including New England Patriots linebacker Junior Seau, Pittsburgh Steelers centre Mike Webster, and New York Giants running back Frank Gifford.
The verse, one of the most quoted from the bible, states whoever believes in Jesus "should not perish, but have everlasting life".
The station also reported that another inmate, a friend of Hernandez's who was one of the last to see him, is under suicide watch at the prison's health service unit.
"No one is going to stand in the way of the family's wishes for Boston University to have Aaron Hernandez's brain", he said.
Authorities said that Hernandez, 27, did not leave a suicide note and was not under suicide watch at his MA prison, where he had been since his 2015 conviction of the 2013 death of Odin Lloyd. He was now serving a life sentence for the murder of Odin Lloyd.
If you or someone you know is contemplating suicide, call the National Suicide Prevention Lifeline 1-800-273-8255.
The former New England Patriots tight end was pronounced dead at UMass Memorial-HealthAlliance Hospital in Leominster about an hour later.