A guard was assaulted by an inmate at a prison in southwest Iowa Monday night.

It happened just after 6:30 p.m. at the Clarinda Correctional Facility. State prison officials, in a news release, say the correctional officer was performing his routine duties at his station when he was confronted by the inmate, who “unexpectedly” began punching the officer.

The guard used pepper spray to gain control of the inmate as other prison workers arrived to help. The officer was taken to Clarinda Regional Health Center for evaluation and treatment and was released later Monday night.

The names of the guard and the prison inmate have not been released.