An ex-Marine was arrested yesterday for killing his stepfather during a brawl that included the accused man giving an “atomic wedgie” to the bloodied victim, who was on all fours in the living room of his Oklahoma residence.

Brad Davis, 33, was charged yesterday with the December 21 murder of Denver St. Clair, with whom Davis had been drinking beer and eating deer chili, according to a probable cause affidavit filed Tuesday in Pottawatomie County District Court.

Davis told police that he began arguing with St. Clair when the older man “began speaking ill of his mother.” A physical confrontation ensued, and Davis repeatedly pummeled St. Clair to the ground, investigators charge.

Davis told cops that St. Clair was “still moving and moaning” when he “grabbed St. Clair’s underwear and gave him an ‘atomic wedgie.’” The probable cause affidavit notes that, “Upon clarification, Davis said he pulled St. Clair’s underwear up over St. Clair’s head.”

Police reported that St. Clair suffered “multiple blunt force injuries to the face” and that his “elastic underwear waistband had been stretched up over his head and left a ligature mark around St. Clair’s neck.”

In a subsequent report, a state medical examiner ruled that St. Clair’s cause of death was “homicide due to blunt force trauma and/or asphyxiation.”

Pictured above, Davis is jailed without bond. He faces a maximum of life in prison if convicted of the murder count.