A dog killed a woman and attacked a man in the Canberra suburb of Watson in the early hours of Wednesday morning.
The woman, who lived at the house and was in her late 40s, died at the scene while the man was rushed to hospital after being bitten on the leg.
About 3.40am, police were called to the home when neighbours heard a man calling for help.
Detective Acting Superintendent Tony Crocker said the man led police into the home, but officers were then attacked by the dog as they attempted first aid on the female victim inside.
Police were forced to shoot the animal dead, but officers were not injured, Superintendent Crocker said.
It is understood the man was visiting the woman when the animal, which is believed to have lived at the home, attacked the pair.
Police were investigating the death and whether the dog is known to authorities. The breed of the dog is not yet known.
Neighbour Dieu Do said she was woken in the middle of the night to the sounds of a man bellowing for help and then, a short time later, gunshots.
Other neighbours expressed their shock at the attack on their "usually quiet street" and said they had often heard a dog growling and barking at the property in recent months. Ms Do said she was afraid a dog on the property might attack her two children.
"A dog, [I think] it was from there, jumped over my back fence a few times last year and almost got my boys," she said. "I often hear [a dog] growling near my window, so I always lock up."
A neighbour, who called police when he heard calls for help from the property, said if the dog was dangerous then he was "glad it's gone" as he also had young children at home.
Detective Crocker said the male victim of the attack was taken to hospital with non-life-threatening injuries where he remained in a stable condition. Police will prepare a report for the coroner.
ACT opposition leader Alistair Coe expressed his deepest sympathies for the family of the woman on Wednesday morning. He also thanked the officers who attended the incident.
"While there are serious questions that need to be answered, our immediate concerns are for those involved in the incident," he said.
Mr Coe said the opposition had requested an urgent briefing from the responsible ministers.
A Transport Canberra and City Services spokesman said there were 389 reported dog attacks in the territory during the 2016-17 financial year, and 14 dogs were declared dangerous.
The Canberra Liberals have been lobbying for laws to make it easier to punish the owners of dogs that attack people or pets.
On August 5, 2017, two puppies survived a mauling from three large dogs that jumped the fence of their Wanniassa backyard.
The next day, a 12-year-old poodle was bitten on the neck and the head by two off-lead pit bulls while running with his owner.
In November 2015, Staffordshire bull terriers tore through Brenda Goldstraw and Jodie Sutton's screen door at their north-west Canberra home. The dogs shredded the hand of 20-year-old Isabelle Goldstraw and mauled the couple's chihuahua Jiminy.
Another attack in the same month left a child traumatised after he witnessed a dog, which had been declared dangerous in NSW, rip out the eye of his grandparents' dog in his family's backyard.
In 2010, six-year-old Jack Hartigan was mauled by two dogs who played tug-of-war with his body at a government housing property. Jack and his family later lost a case against the ACT government over the attack.