WALLA WALLA — A nurse at the Washington State Penitentiary suffered minor injuries Wednesday after being assaulted by an inmate during a medical examination.

The assault occurred at about 11:30 a.m. in one of the prison’s West Complex close-custody units. The prisoner, Steven D. McDonald, 58, “was having his blood pressure taken by the nurse when he became agitated and struck the nurse once in the temple,” said Selena Davis, Department of Corrections spokeswoman.

McDonald was restrained by correctional officers, who had to use pepper spray to bring him under control, Davis said in a release.

The unit where the assault occurred, Delta Unit, was placed on lockdown Wednesday night, but was back to normal status this morning.

According to Davis, McDonald is serving a life sentence without parole. He was sentenced under the state’s “three strikes” law in 2002 after being convicted of two counts of arson in Skagit County.