An investigation is under way at the Cobb County Adult Detention Facility after an inmate died.

Jail staff found Robin Tracy Harrington unresponsive in his cell at 10:30 p.m. Sunday and began CPR on him.

Harrington was taken to Kennestone Hospital and was pronounced dead at about 11:30 p.m.

It is unclear what caused Harrington's death, but Cobb County Sheriff Neil Warren said there is no indication there was foul play involved.

The Sheriff's Office Inspectional Services Division, with assistance from the Georgia Bureau of Investigation and Cobb County Medical Examiner's Office, is conducting an investigation.

Harrington had been serving three life sentences after he was found guilty of a rape at the Woodhollow Apartment complex on Powers Ferry Road in Marietta in 2003.

At the time of the rape, Harrington was a door-to-door salesman, police said. Police said he may have used his employment at that time as a ruse to contact victims.