EUGENE, Ore. – Three shots fired at a federal courthouse in Oregon late Wednesday or early Thursday hit windows in U.S. Rep. Peter DeFazio’s office, while a fourth shot hit a wall above the office, the FBI said.

No one was in the second-floor office at the time, and the Democratic congressman’s staffers in Eugene found the damage when they arrived for work Thursday morning.

Investigators believe the shots were fired between 9:30 p.m. Wednesday and 7 a.m. Thursday, FBI spokeswoman Beth Anne Steele said, adding they’re not certain that DeFazio’s office was the intended target.

“Right now, our biggest concern is determining why this happened,” Steele said, adding the FBI doesn’t know whether the shooter or shooters were trying to hurt anyone.

DeFazio spokeswoman Molly Simmons confirmed the congressman was in Washington, D.C., at the time.

The Register-Guard reported that from outside the courthouse, the only visible damage to DeFazio’s office was to one window that had a single, quarter-sized hole with cracks spidering outward.