An Orangeburg man has admitted conspiring to kill a prison guard in a hit orchestrated by an inmate on an illegal cellphone.

U.S. Attorney Bill Nettles says 30-year-old Sean Echols pleaded guilty Wednesday to conspiracy to use interstate facilities in murder-for-hire. He faces up to 20 years in prison.

Capt. Robert Johnson was shot six times at his Sumter home in 2010. Police say an inmate organized the hit using a cellphone smuggled into Lee Correctional Institution, where Johnson oversaw efforts to keep out such contraband.

Johnson survived. Authorities say je was the first U.S. corrections officer harmed by a hit ordered from an inmate's cellphone.

Echols is currently serving a 25-year prison sentence for armed robbery and assault. Authorities have not named the inmate who allegedly organized the plot.