The (Albany, Ore.) Democrat Herald said three of the shots struck windows in the office of Rep. Peter DeFazio, D-Ore., and the fourth hit a wall above the office, apparently Wednesday night or Thursday morning.
No injuries were reported.
Investigators were unsure if DeFazio's office was the intended target , the Democrat Herald said.
The damage to the office was discovered by DeFazio's staff.
The Eugene Police Department, U.S. Marshals Service and Federal Protective Service aided the FBI in the investigation, the newspaper reported.