According to WUSA9, the shooting occurred in Woodbridge at the 3500 block of Buffalo Court.
The employee sustained "serious" but non-life-threatening injuries, the outlet said. Prince William County Police reported that the suspect was a Black male who wore a light-colored shirt, dark pants, and no shoes.
It's unclear what prompted the shooting but the incident came just after another USPS employee was shot and critically injured in Chicago.
The US Postal Inspection Service is currently offering up to $50,000 in rewards for information leading to the arrest and conviction of the suspect in that shooting.
For weeks, controversy has swirled around the U.S.P.S. and its activities prior to the upcoming elections. Police said it didn't seem as though the Chicago victim was targeted, according to Channel 3000.
The USPS did not immediately respond to Fox News' request for comment.