The Oakland County Sheriff's Office responded to reports of shots fired on West Huron Street Monday evening.
When deputies arrived at the scene, they found two broken front windows on the north side of the United State Postal Service. A third window remained intact but had "an obvious bullet hole in it."
Police say there were two postal workers and two customers inside the building at the time the windows were broken.
Authorities are not sure if the Post Office was the intended target.
According to Postal Inspector Wylie Christopher, the shots did not come from inside of the building, and there were no injuries. He added that investigators do not believe postal workers were targeted.
County Sheriff's and the Postal investigators are still investigating the incident.