A grand jury cleared a Prince George's County police sergeant yesterday of criminal misconduct in the shooting death of a Louisiana man who investigators said attacked the officer with a knife after a collision on a Capital Beltway exit ramp in Bethesda.

The grand jury in Montgomery County found no evidence of wrongdoing by Sgt. Benny G. Gilbreath, who was off duty the morning of Dec. 12 when he shot Richard F. Calvird five times as Calvird moved toward him with a hunting knife, according to the Montgomery County state's attorney's office and the police detective who investigated the shooting.

The detective, Daniel Waring of the Montgomery police, said Gilbreath was not in uniform but did identify himself as a police officer before shooting Calvird "in the upper body area." According to the detective, an autopsy showed that Calvird was intoxicated at the time of the shooting.

Waring said Calvird, 38, driving a pickup truck, sideswiped Gilbreath's van while trying to cut in front of the van as both vehicles drove off the Beltway to an exit ramp leading to Rockville Pike in North Bethesda.

Calvird then rammed his pickup truck into the rear of the van, and "charged" at Gilbreath with the knife after the officer got out to inspect the damage, Waring said. He said Gilbreath reached into the van for his .38-caliber police revolver in his holster beside the driver's seat.

"There wasn't really much time," Waring said. "He leveled at the guy and yelled, 'Police!' But by that time they were within arm's reach. He fired five shots and dropped the guy."

Calvird, from Kenner, La., had been employed at a Prince George's construction site. He had a blood-alcohol level of 0.19 percent when he died, Waring said.

Under Maryland law, the detective said, a motorist whose blood-alcohol level is 0.13 or higher is considered to be driving while intoxicated.

The results of toxicology tests, which will show whether Calvird used drugs before the shooting, have not become available yet, Waring said.

Gilbreath, a 16-year veteran of the force, was placed on routine administrative leave, but returned to duty Dec. 15 after his department's internal affairs unit determined the shooting was "justified and proper," said Cpl. Bruce Gentile, a Prince George's police spokesman.

The Dec. 12 fatal shooting was the third in a three-week period involving off-duty police officers in Montgomery County.