RICHMOND HEIGHTS, Mo. – An investigation is underway after a Richmond Heights post office was robbed at gunpoint Thursday night.

Officers responded to the post office at 1209 S. Big Bend around 5:40 p.m.

The post office was closed at the time, but employees were still in the building. No one was injured, police said.

It’s unclear exactly what the suspect got away with, but the post office said the suspect took U.S. Postal property.

The United States Postal Inspection Service said the suspect, a man, was wearing all black clothing, a mask and was armed with a gun when he entered the post office.

The United States Postal Inspection Service is offering a reward of up to $50,000 for information leading to the arrest and conviction of the unknown suspect.

Anyone with information that could lead to the identification of the person of interest should contact 314-539-9361.