Neighbours say they heard shouts and screams coming from a Gordon house where a 28-year-old mother-of-two was found dead with stab wounds in the early hours of Tuesday.
The woman's death prompted police to launch their third homicide investigation in the ACT in the past three weeks.
One of the deaths under investigation was that of alleged murder victim Tara Costigan, who was also 28 and had three young children when she died.
Ms Costigan's death prompted an outpouring of grief from the community after she was allegedly killed by her former partner in Calwell on February 28.
Police were called to the Knoke Avenue house in Gordon after reports a woman had been killed about 3.10am on Tuesday.
They discovered the victim in a bedroom with critical head injuries and several stab wounds. She was pronounced dead at the scene.
ACT Policing acting Superintendent Harry Hains said no one else had been inside the house when police and paramedics arrived.
"As with any crime scene, it was horrific," acting Superintendent Hains said.
"The woman suffered significant stab injuries and obviously that speaks for itself."
A man was helping police with their investigation but no charges had been laid on Tuesday night.
Police would not be drawn on the relationship between the man and the woman.
"At this stage he is not a suspect, he is just assisting police," acting Superintendent Hains said.
Neighbours said a couple and two children had moved into the public-housing townhouse in the past year.
Duncan Kidston, who lived behind the house, said he had heard screams and cries in the middle of the night. He had also heard arguments in the house previously.
Neighbour Frances Ottewill said she didn't know the woman but had called police after she heard a loud argument at the house several weeks ago.
Several neighbours said they hadn't heard anything suspicious overnight and only learned of the alleged killing when police showed up on Tuesday.
Play equipment and toys were littered throughout the home's backyard, and residents in the complex behind the house said the children often played with other youngsters who lived nearby.
A neighbour who used to live in the house next door said the woman had stayed at home and was often seen walking her children to and from school.
"She was very lovely. She was very quiet.
"Nobody was close to her, she kept to herself. When I'd see her she'd just nod her head."
The neighbour said she intended to buy a bunch of flowers to lay near the woman's house.
Manuara Morgan, who has lived on the street for five years, was shocked by the death.
"I always see kids playing out the front, but I've never heard anything [suspicious]," Ms Morgan said.
Another neighbour, who did not want to be named, was also surprised by the death.
"It's a quiet area with no major crime, just occasionally some hoons," she said.
A section of Knoke Avenue and Matson Street was taped off and closed to traffic on Tuesday morning as AFP forensics crime scene investigators examined the crime scene.
Police said a weapon hadn't been identified.
Two men have each been charged separately with murder in relation to those incidents. The three deaths are not connected.
The Gordon woman's death was the second gruesome incident to take place in the otherwise quiet suburban street on Canberra's southside in little more than a decade.
Susan Winburn, 45, was found strangled to death in the bathtub of her Knoke Avenue home in January 2004. Her murder has never been solved.
Police are urging anyone who may have witnessed the Gordon incident on Tuesday or can provide information and has not yet spoken to police to contact Crime Stoppers on 1800 333 000 or via act.crimestoppers.com.au.