The Nebraska Department of Correctional Services says 71-year old Decabooter Williams died Tuesday morning at the Tecumseh State Correctional Institution.
His sentence began in June, 2004.
He was serving a life sentence for two counts of first degree murder out of Douglas County.
Williams was convicted in the 2003 deaths of Victoria Burgess and Latisha Tolbert in a house fire prosecutors say Williams started after an argument.
Corrections says while the cause of death has not yet been determined, Williams was being treated for medical conditions.
As is the case whenever someone dies in custody or while being taken into custody, Nebraska law mandates a grand jury investigation.
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