Palmer police are investigating an armed robbery that happened shortly after 9 a.m. Saturday at the post office in Thorndike.
Police say a white male threatened the clerk with a knife, took money from the register and fled in an unknown direction on Church Street.
The postal worker was not injured.
The U.S. Postal Service and the Massachusetts State Police are assisting in the investigation.
The Postal Service is also offering a reward for any information leading to the arrest and conviction of the suspect.
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