LINCOLN, Neb. -- A Dawson County man died during his sentence at the Nebraska State Penitentiary on Wednesday.

According to officials, 69-year-old Daniel Holliday was serving a sentence of 30 to 35 years for charges in Dawson County. He was reportedly charged with two counts of first-degree sexual assault and one count of visual depiction of sexually explicit conduct.

NSP said the cause of death has not been determined yet. Whenever an inmate dies in the custody of the Nebraska Department of Correctional Services (NDCS), a grand jury will begin an investigation.