A Prince George's County police sergeant who fatally shot a Louisiana man on the Capital Beltway last weekend was allowed to return to work yesterday after an internal investigation found nothing wrong with his action, authorities said.

Sgt. Benny Gilbreath was placed on administrative leave with pay after he fatally shot another motorist on I-495 near Wisconsin Avenue in Bethesda about noon Saturday.

Richard Calvird of Kenner, La., allegedly rammed his pickup truck into the rear of Gilbreath's car twice before the shooting, said Harry Geehreng, a spokesman for the Montgomery County Police Department.

The second time he was rammed, Gilbreath, who was off duty and driving with his wife, pulled onto the shoulder of the highway and Calvird stopped behind him, Geehreng said.

When the man got out of his truck and approached the sergeant with a knife, Gilbreath pulled out his service revolver and shot him, police said. Calvird was pronounced dead at the scene.

"A thorough review by the county police department and conversations with representatives of the state's attorney's office . . . concluded that the actions of Benny Gilbreath were justified, lawful and proper," said Prince George's County police spokesman Bruce Gentile. "He is back on regular duty."

Gilbreath is assigned to the police department's special operations division.