The Prince George's County police department has launched an internal investigation into the conduct of an officer who went after a man in the hallway of a courthouse Thursday and then ignored a court security officer who told him to move away, two police sources said.

Cpl. Frank Perrus, who joined the department in 1991, is under investigation in connection with the incident, which occurred in U.S. District Court in Greenbelt, according to the sources, who spoke on condition of anonymity because they are not authorized to discuss personnel matters.

Maj. Andrew Ellis, a police spokesman, confirmed an officer is under investigation for his conduct at the courthouse, but he declined to provide the officer's name because it is a personnel issue.

Perrus declined comment through Vince Canales, president of the Fraternal Order of Police Lodge 89, which represents rank-and-file county officers.

Jacques Chevalier, 55, said he believed that Perrus would have assaulted him if the federal court security officer had not intervened. "I was intimidated," Chevalier said.

A Washington Post reporter witnessed the encounter.

Perrus was one of about 15 county police officers who went to court to support Sgt. Richard Delabrer, who is charged with conspiracy in a scheme to smuggle untaxed cigarettes and alcohol into Maryland. Delabrer's arrest is part of a broad federal investigation into corruption in Prince George's, a probe that became public last week when County Executive Jack B. Johnson and his wife, Leslie Johnson, were arrested on charges of evidence tampering and destruction of evidence.

Delabrer had been scheduled for a detention hearing Thursday afternoon, but it was postponed.

Perrus and the other officers, all in civilian clothes, gathered in the hallway outside the courtroom.

Chevalier, who often attends trials in the county in which police or public officials are accused of crimes, stood about 15 feet from the officers, took out his cell phone and made a call.

Chevalier said he told a friend that he was happy that Delabrer would remain locked up. He acknowledged that he used a slur for a homosexual when referring to Delabrer.

Chevalier said Perrus challenged him, saying, "Who are you looking at?" and walked toward him. At that point, Chevalier began walking away.

Moments later, Chevalier stopped and turned as Perrus stepped close to him. A court security officer - a retired D.C. police officer - quickly stepped between the two.

Three times, the court officer directed Perrus to walk away, and Perrus ignored him. Finally, a member of Perrus's group came over and walked the corporal back.