The officer was part of a mounted patrol overseeing a work crew of prison inmates, who were working to clear grass and brush around the prison.
According to DOC spokeswoman Shea Wilson, the inmate, Joseph Henry, 39, of Benton County, became unruly during the work detail, and attempted to attack the officer on horseback as other officers tried to subdue him.
Henry was released from the Calico Rock prison in 2006 after serving a sentence for second-degree battery and terroristic threatening.
He was returned to the prison in 2009, when his parole was revoked after he was charged with a new crime. In March, Henry was given a 21-year sentence after being convicted of two rapes.
Henry may face additional charges related to the Dec. 19 prison incident.
DOC is currently investigating the shooting and events to determine whether correction officers overseeing the work crew followed proper procedures.
Henry was hospitalized after being shot in the upper right shoulder and was still hospitalized on Dec. 20, but was expected to be returned to prison in a few days.