A man armed with a knife threatened staff at a Northampton bank before jumping over the counter and stealing cash.
The incident at the Santander branch in Mercers Row, opposite All Saints Church, at about 5pm on Monday December 30.
A spokesman for Northamptonshire Police said the man then ran out of the public exit.
“The man is described as white, 5ft 7ins with blue eyes. He was wearing grey jogging bottoms, a black woollen hat and a black scarf across his face. He was carrying a rucksack.
“Witnesses to this incident, or anyone with information, should call Northamptonshire Police on 101 - alternatively, information can be given anonymously to Crimestoppers on 0800 555 111,” the spokesman added.