An elderly man sustained serious facial injuries after a burglar armed with a hammer pushed his way into his Northampton home.
The 79-year-old man had answered the door of his home in Trussell Road, Bellinge, to a man who claimed to be from the police.
The offender threatened him with a hammer, demanded a code for a safe and assaulted him.
He stole property and used a bank card in Blackthorn to withdraw cash.
The offence took place between 0620 and 0635 BST on Wednesday.
'Defenceless and vulnerable'
The burglar is described as white, about 5ft 10in (1.78m) tall and skinny.
He was wearing a black woollen hat and a light grey tracksuit top with three turquoise stripes running from the collar down each arm.
The tracksuit bottoms were also light grey with three turquoise stripes running from the waist to the ankle.
He was wearing dark-coloured trainers with white soles.
A spokesman for Northamptonshire Police said: "This was a particularly nasty incident which resulted in a completely unnecessary attack on a defenceless and vulnerable elderly man.
"If you recognise the offender from the description or noticed any suspicious activity in the Bellinge, Billing and Blackthorn area of the town early Wednesday morning then please contact us a matter of urgency."