North Yorkshire Police said Diane Garbutt, 40, was found dead in the upstairs living quarters of the village store, in Melsonby, near Richmond, at about 8.30am yesterday.
Today, detectives leading the inquiry revealed Mrs Garbutt had died from severe head injuries but could give no further details as to how this happened, apart from confirming she had not been shot.
Detective Superintendent Lewis Raw said Mrs Garbutt's husband Robin had been working downstairs in the shop since 4.30am when he was confronted by the raider, who eventually left with a substantial amount of money in a holdall.
Mr Raw confirmed his officers were called to the post office by the ambulance service at 8.38am.
He said the paramedics were called by Mr Garbutt, 44, who found his wife upstairs.
The detective said he did not to give any further details about where the body was discovered.
Mr Raw said Mr Garbutt had opened the shop part of his business as normal at 4.30am, leaving his wife upstairs.
He was disturbed by the raider just after he opened the post office counter at 8.30am, he said.
The detective said the suspect came into the shop from the living quarters.
Mr Raw said: "The man threatened Mr Garbutt, saying 'we've got your wife'.
"The male then made off with a significant amount of money, which he had placed in a black holdall."
The suspect was described by Mr Raw as 5ft 11in to 6ft tall, wearing a black, tight-fitting mask, a dark blue, long-sleeved T-shirt and dark blue-black coloured jeans.
He added: "He was carrying a firearm at his side."
The detective appealed for anyone who was in Melsonby between 4am and 9am to contact him if they saw anything suspicious.
The suspect or suspects left the premises between 8.30am and 8.38am.
He said: "This would have been a fairly busy time in the village, with people travelling to work or school.
"We are appealing for anyone who may have seen a suspicious or unknown vehicle in the village, or saw one leave the village at that time, or if you saw a man dressed in dark clothing and wearing a mask to come forward."
He also asked people to be on the look-out for any discarded balaclavas.
Mr Raw said: "This is a shocking crime, which has left Mr Garbutt distraught and the residents of Melsonby very shocked and saddened.
"Police are determined to bring Mrs Garbutt's killer to justice. However, we need the assistance of members of the public who were in the area at the time to come forward."
People living and working around the post office said they did not notice anything unusual yesterday until an ambulance and then armed police arrived.
Bill Nixon, who owns Nixon's Garage opposite the post office, said he was at the garage at the time but did not hear anything out of the ordinary.
He said: "I was just here and all the kids were down there, about 38 to 40 kids. They get their sweets and that from the shop.
"I had a contractor coming to see me. I told him to park his van across the road and then I had another customer and within a few minutes I heard the ambulance come. I thought 'That's strange', then all hell broke loose."
Linda Ling, who works part-time in the shop and lives in a nearby cottage, also said she did not see or hear anything to suggest a disturbance.
She said: "I never heard a thing. I opened my curtains around 8.15am and saw the kids waiting for the bus, went to make my bed and then saw the ambulance."
Ms Ling said she thought Mr and Mrs Garbutt had been married for around five or six years and added: "A dead lovely couple, just very devoted, that's all I can say.
"I feel very sorry for Robin, I don't know how he'll go on without her."
Officers questioned drivers and members of the community in Melsonby this morning.
Long queues of traffic formed on the routes into and out of the village as police stopped vehicles to try to gather witness statements.
People walking past the stone-built post office were also spoken to by officers investigating the murder.
Around 30 bouquets of flowers had been laid at the scene and children with parents on the morning school run handed over more floral tributes to officers.
The road surrounding the post office was closed and cordoned off and police officers, vans and cars were at the scene.
Mr and Mrs Garbutt's business, called The Village Shop and Post Office, is at the heart of the small village, a few miles north of Richmond.
It is thought the couple moved to Melsonby about seven years ago from the York area.
Police said the store was targeted by armed robbers in March last year, when two men, one armed with what appeared to be a handgun, threatened staff and made off with stamps and a large amount of cash.
People in the village said the couple considered leaving the village at the time of the raid and put the business up for sale but, it appears, they had recently decided to stay.
Members of the close-knit community said they were shocked by Mrs Garbutt's death.
One woman, who did not want to be named, said: "They were the nicest people you could ever meet, the most genuine people.
"All the kids round here just loved them."
Mr Raw said a team of around 30 officers was working on the case.
He said: "At this stage the only report in relation to the firearm is from Mr Garbutt when he reported the man carrying the firearm by his side.
"She (Mrs Garbutt) was not shot, I can confirm that to you."
Asked about the raid on the post office a year ago, Mr Raw said: "Obviously there are similarities with the crime that we are investigating at the moment and that is a line of inquiry that will be progressed
"There was an extensive investigation done at the time, an imitation firearm was recovered but, in respect of that offence, nobody was arrested."
The detective added: "Obviously Mr Garbutt is distraught in relation to what's happening.
"He has helped us from the start of the inquiry and provided us with information and we'll do everything we can to support him throughout this investigation."
Mr Raw said Mr Garbutt had been serving customers in time before the raider appeared and he appealed for them to come forward.
He could not confirm whether children had been in the shop immediately prior to the incident.
The officer said Mrs Garbutt, who is understood to have a military background, "will be badly missed by her family and the community."
