The Nebraska Department of Correctional Services says 52-year old Jose Cabrera-Lomeli died at the Reception and Treatment Center in Lincoln.
He was serving 160-220 years for numerous counts of first degree sexual assault of a child in a case out of Sarpy County.
He was sentenced last October.
Corrections says, while the cause of death has not yet been determined, Cabrera-Lomeli was being treated for a medical condition.
Under Nebraska law, a grand jury will investigate the death.
(Picture from Nebraska Department of Correctional Services)