A 23-year-old Silver Spring man, who was charged with second-degree murder in the shooting deaths of two District men, has been charged with first-degree murder in the July 7 death of a Northern Virginia man who was shot in the head and chest while driving near Rte. 50 in Arlington, police said.

Arlington police said they arrested Deonicio N. Vivar of 8670 Piney Branch Rd. and charged him with murdering John P. Green, 39. Vivar is being held in Arlington jail on $250,000 bond.

Both Arlington prosecutor Lian O'Grady and Vivar's court-appointed lawyer, Richard J. McCue, said yesterday that Vivar had been freed on personal recognizance after his arrest Dec. 15 in the deaths of two men who were killed earlier that day on Columbia Road NW.

Arlington police said the same gun used in the District shootings is believed to have killed Green, of 1501 N. Pierce St., Arlington. He was driving his pick-up truck on N. 10th Street when he was shot. Police have said a traffic altercation may have prompted the shooting.

A witness initially told police that one of two men in a dark green Volvo shot Green, but police said yesterday the investigation has focused on other cars as well.

Arlington police said they are seeking a second suspect.

Vivar, a construction worker for a Germantown firm, was arrested April 19, but Arlington police withheld the news, a spokesman said.