Police Chief Shawn Schwertfeger identified the gunman as Thomas J Piccard, 55, of Bridgeport, Ohio. He was a retired Wheeling police officer.
Schwertfeger did not say whether Piccard used both weapons during the assault on the Wheeling Federal Building yesterday or speculate on a motive.
Officials said they had no knowledge of any sort of note left behind by Piccard. Flying debris injured three on-duty security officers during the onslaught, he told a news conference.
Mayor Andy McKenzie said police who briefed him earlier yesterday told him that Piccard was a 20-year-plus veteran of the force who retired 13 years ago.
Investigators were seeking a search warrant for Piccard's home in hopes of determining a motive and if he acted alone, said Chief Deputy Mike Claxton of the US Marshals Service in northern West Virginia.
Asked if the gunman had any beef with the US government, Claxton said, "We're really digging hard at this point to find out." Claxton said a man later identified as Piccard began firing from a parking lot across from the federal building.
"He was observed in the parking lot very quickly after the first shots were fired," he said. The building houses a variety of courtrooms and related offices, including those for judges, prosecutors and law enforcement.
Officials said it was too early to tell whether Piccard was targeting anyone in the building or what his motive may have been. "That's still trying to be determined," said Bob Johnson, the assistant special agent in charge of the FBI's Pittsburgh office.
People inside the building ducked under desks as the shots struck the building and shattered windows. US Attorney Bill Ihlenfeld said shots were fired into at least three rooms in his office on the building's second floor.
He described hearing gunshots, then panic among staff. "Members of my staff were crawling on the floor or running from office to office telling people to get away from the windows," he said.
Ihlenfeld said he knew Piccard from 1997 when he started working in the city prosecutor's office until the officer retired in 2000.
He said he had no reason to believe his office was targeted, and that Piccard was not under any sort of investigation by federal authorities.