Marion County Coroner Norma Williamson said Deputy Paul Hooper died from a gunshot wound in the chest Sunday outside a home in the county.
Authorities say Greg Elkins has been charged with murder. Elkins was being held Tuesday on a $500,000 bond in the Lamar County Jail. Elkins is a former captain with the Columbia Police Department.
A news release from the Marion County Sheriff's Department says Hooper was living with the suspect and the motive for the shooting is still under investigation.
The Mississippi Highway Patrol is handling the investigation.