BOSTON (WHDH) — At least one Department of Corrections officer is facing disciplinary action in connection with the suicide of ex-NFL star Aaron Hernandez.

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Sources tell 7News that a correctional officer at the Souza-Baranowski Correctional Center in Lancaster, Massachusetts, has been disciplined for missing a 2 a.m. walkthrough on Wednesday, just one hour before Hernandez was found hanging from a bed sheet in his cell.

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.

Gov. Charlie Baker said the state would conduct an investigation to make sure “everyone knows exactly what happened and when.”

Hernandez was not on a suicide watch. His death came just five days after he was acquitted of a double-murder charge. He was serving a life sentence for the 2013 shooting death of a onetime friend, though his legal team had plans to appeal the conviction.

Investigators are reviewing surveillance video from inside the prison. They are interviewing inmates and prison guards that may have had contact with Hernandez.

The suicide left friends, family and his legal team shocked and in disbelief.

The officer in question has not yet been identified.

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