Police say a South Carolina man charged with sexual assault of his nephew's girlfriend was beaten by the relative, who won't be charged in the incident.

Fifty-two-year-old William Mattson of Conway is charged with first-degree criminal sexual conduct. Local media outlets report that a judge denied him bond Saturday.

Mattson was arrested New Year's Day. Authorities say Mattson's nephew told them he came home and found his girlfriend and uncle in bed together. The nephew said the woman was naked, and Mattson was clothed.

The man said he beat Mattson until he was out of the house. Authorities say the nephew won't be charged because he was defending the woman.

Mattson was jailed Monday. It wasn't known whether he had an attorney. Authorities say he's scheduled for a March 20 court appearance.