A post office worker was hit with a hammer and his family threatened with a knife during a robbery in Northampton on Thursday afternoon.
The two attackers wrestled the man to the floor at Broadmead Avenue Post Office and demanded the keys to the post office counter.
He was hit on the arm with the hammer before handing over the keys. The two robbers then stole cash from the till.
The offenders ran off after they were disturbed by relatives of the victim.
Police said he was treated for minor injuries by paramedics but was left very shaken by the ordeal.
Both offenders were believed to be Asian. One was about 5ft 3in tall with a slim build and wore a black face mask, a hooded top, grey jogging bottoms and blue gloves.
The second was about 5ft 3in tall and of a medium build. He was 18 or 19 years old, had a small, thin moustache and wore a blue hooded top and jogging bottoms.