A Charleston man on Friday withdrew his not guilty plea to two counts of a federal indictment against him that resulted from an investigation of the sale of sex with a minor.

Booker T. Vanderhorst, 66, was scheduled to go to trial in U.S. District Court next week. He pleaded guilty Friday to use of interstate commerce to promote an illegal activity and possession of a firearm by a prohibited person. In exchange, the government said it would drop one count of the indictment which charged him with sex trafficking of children.

Vanderhorst, who is tall, thin and wears glasses, appeared in court dressed in gray and white prison stripes. He was shackled at the wrists and ankles,

He said “Yes, sir” repeatedly to Judge Michael Duffy’s questions regarding issues such as Vanderhorst’s understanding of the proceedings and whether he was pleading guilty of his own accord. Vanderhorst told Duffy that he finished high school and attended college for a while.

Duffy said his final acceptance of the plea agreement would hinge on his review of a pre-sentencing report. As part of the deal, Vanderhorst would face a possible sentence of up to 60 months on the two counts to which he pleaded guilty. Otherwise, he could receive up to 15 years on those two charges.

Sex trafficking of children carries a mandatory minimum sentence of 10 years, and a maximum term of life imprisonment.

According to Assistant U.S. Attorney Nathan Williams, Vanderhorst was operating an escort service when he met a 17-year-old minor girl and on several occasions drove her to area locations where she performed a sex act for pay. Afterwards, Vanderhorst and the girl split the money.

“She worked under his control and his guidance,” Williams said.

Between July and October 2012, Vanderhorst prostituted a minor female he knew to be under the age of 18, according to the indictment.

He was arrested without incident in April 2013 by U.S. Immigration and Customs Enforcement’s Homeland Security Investigations.

The young woman is a U.S. citizen, Williams said.