Hernandez, 27, was discovered hanging in his cell by corrections officers in Shirley, Massachusetts at approximately 3:05 AM today, Christopher Fallon with the Massachusetts Department of Correction said.
"Mr Hernandez hanged himself utilising a bedsheet that he attached to his cell window," Fallon's statement said.
"Mr Hernandez also attempted to block his door from the inside by jamming the door with various items."
Lifesaving techniques were administered to the former New England Patriots tight end and he was rushed to a hospital, where a physician pronounced him dead at approximately 4:07 AM.
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Hernandez's death comes on the same day that President Donald Trump will host his former team the Patriots -- which won the premier American football championship, the Superbowl, in early February - at the White House.
"We are aware of the reports, but don't anticipate that we will be commenting today," a Patriots official told The Boston Globe.
Hernandez was serving a sentence of life in prison without parole for murdering Odin Lloyd, a semi-pro football player, in June 2013.
His 2015 conviction had cemented a spectacular fall from grace for Hernandez, who once had a $40 million, five-year contract with the Patriots.
His death also comes five days after he was cleared of killing two men in a drive-by shooting in July 2012 in Boston's South End after an altercation outside a night club.
The jury acquitted Hernandez on seven of eight charges after reportedly deliberating for 37 hours, and he was convicted only on an illegal firearms charge.
At the time Hernandez, who had pleaded not guilty, was overcome with emotion as the verdict was read, moving his head from side to side, wiping his eyes and weeping.
On Twitter, some people said the timing of his death was strange because he had just been cleared of the two killings.
Others emphasised that he was a convicted murderer who deserved no pity.
"He was such a good NFL player. Imagine what Aaron Hernandez could have been... RIP," one fan tweeted.
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