LINCOLN, Neb. -- Authorities reported the death an 88-year-old inmate who was serving time for the sexual assault of a child out of Custer County.

The Nebraska Department of Correctional Services said that 88-year-old Floyd Martin died Sunday at the Reception and Treatment Center, where he was incarcerated. 

Martin started his 35 to 40 year sentence Nov. 6, 2008. He was serving time for the second-degree sexual assault of a child out of Custer County. 

While the cause of death has not yet been determined, NDCS said that Martin was being treated for a medical condition. 

As is the case whenever an inmate dies in the custody of the NDCS, a grand jury will conduct an investigation.