The robbery took place at 7:15 am in the morning on Tuesday.
The thief attacked a 56 year old U.S. postal worker on her head with a gun.
The gunman ordered the woman to open the safe.
The thief has stolen around $100k in cash and blank money orders.
He then ran away from the postal office in a white minivan.
The incident was recorded in a nearby security camera.
The police is still investigating and trying to catch the culprit.