The body of the man in his 70s, was found at the house in Nettleden Road, Little Gaddesden, near Berkhamsted, on Saturday afternoon.
A man in his 80s was also taken to hospital, a police spokeswoman said.
Detectives want to question 55-year-old Ian John McLoughlin, also known as Ian John Baker, and have warned people not to approach him.
Det Ch Insp Martin Brunning, from the Bedfordshire, Cambridgeshire and Hertfordshire major crime unit, said: "The investigation is still in its early stages.
"However, we are continuing to treat the death as murder. We urgently want to speak to Ian McLoughlin in connection with this offence."
He is described as white, about 6ft (1.8m) tall, with straight, greying, collar-length hair and of average build.
He is believed to have been wearing sunglasses, blue jeans or three-quarter length trousers and a dark blue, light blue and white checked short-sleeved shirt with a button-down collar.
Anyone with information has been urged to contact police or Crimestoppers.
Officers have been conducting additional patrols in the area to provide reassurance to residents.

Swiss Xhaka, 24, is believed to have been with a friend who had visited him in London and was returning home.
The man is understood to have arrived late for his flight back to Germany and was not allowed to board.
It is at this point that the racial abuse is alleged to have occurred.
Arsenal have declined to comment other than to say it is a private matter that is now in the hands of the police.
A spokesman for the Metropolitan Police told the BBC: "Police were called at 19:29 GMT on Monday, 23 January following an allegation that a member of staff had been racially abused at Heathrow Airport, Terminal Five.
"The allegation was made by a third party. Officers attended and spoke with a man in his 20s. He was not arrested. He voluntarily attended a west London police station where he was interviewed under caution. Enquires continue."
The incident occurred just over 24 hours after Xhaka was sent off during his team's 2-1 victory over Burnley in the Premier League.

About seven miles (11km) of shoreline, including beaches at Great Yarmouth, Gorleston and from Scratby to North Denes, were affected by the flooding.
On Scratby beach alone, it is believed there are about 6,000 sq metres (65,000 sq ft) of waste, 3ft deep (1 metre).
The operation is expected to take several weeks.
Before Christmas, staff from Great Yarmouth Borough Council took away any potentially hazardous material, including gas bottles, fridges and freezers.
Now workers are left with glass, wire and wood to dispose of.
George Jarvis, from Great Yarmouth Borough Services, said a lot of manpower was being used to sift through the debris.
"We did consider burning on the beach, but looking at the weather forecast we're due to have quite a lot of wet weather this week," he said.
"Also the prevailing winds coming in from the sea would have blown quite a lot of thick, black smoke into public areas."
There is no estimate for the total cost of the clear-up, as it is not yet known how long it will take.
The council hopes to recoup the money spent through the government's Bellwin Scheme.
The Bellwin Scheme was introduced in the 1980s to provide some government support for flood-hit areas, but only provides funds for temporary flood measures and the work must be undertaken within two months of the flood.
Police are seeking a man over the murder of an elderly man found dead at a house in Hertfordshire.
[NEXT_CONCEPT]
Arsenal midfielder Granit Xhaka has been interviewed under caution by police following an allegation he racially abused an airline staff member at Heathrow on Monday night.
[NEXT_CONCEPT]
Work has begun to clear up hundreds of tonnes of waste washed up on Norfolk beaches during last month's North Sea tidal surge.