Manurewa mother Arishma Archana Singh likely knew her killer and allowed the person into her home, police say.
Singh, 24, was found dead in her Maich Rd home yesterday.
It has been revealed that Singh, also known as Chand, arrived home from a friend's birthday party at 12.45am on Sunday.
She was with her boyfriend but he did not stay.
Soon after he left the property Singh called her parents Rakesh and Aradhana Singh and said she could hear a noise outside and she was worried.
They were out visiting relatives but rushed home.
When they got inside they found Singh dead.
Detective Inspector Gary Lendrum said there was a 20-minute window between Singh's boyfriend leaving and her parents arriving home.
He said it was not clear what the young mum heard outside, or why she was scared - but a large number of police were now trying to piece together her final minutes.
Addressing media at a press conference, Lendrum said Singh had "obvious injuries" which led them to launch a homicide investigation.
Earlier Singh's family had been told it was possible she had come home and interrupted an intruder.
However Lendrum now believed that was not the case.
He explained there was no forced entry to the Maich Rd house, nothing was disturbed.
That led investigators to believe Singh knew her killer and had let the person into her home.
"We don't believe that this is a random attack," Lendrum said.
"At this initial stage in our inquiry we believe that the offender was known to the victim in some way."
A post-mortem examination will take place today.
Lendrum said that would help police ascertain exactly how Singh died.
"We are quite determined to get to the bottom of this," he said.
Lendrum said police had spoken to Singh's parents, boyfriend and ex-husband.
The Herald revealed last night that Sing and her husband separated amicably three years ago.
They share custody of their three-year-old daughter.
She was with her father as part of their prearranged custody routine when Singh was killed.
Lendrum said Singh's new boyfriend and the rest of her family were being co-operative.
He knew where Singh's boyfriend went after he left Maich Rd but would not be drawn on the specific details.
Police are in the process of collecting CCTV footage from the area and said they would be "trawling through it".
Investigators will also be looking into any family harm or domestic violence issues Singh may have had.
Lendrum wanted to assure the community that there was not a killer "wandering around" their streets.
He had a "gut feeling" Singh knew her killer and allowed that person into her house on Sunday.
"The answer is much closer to home," Lendrum said.
Singh, also known as Archana Chand, was found by her parents lying on the floor of her bedroom "in a pool of blood" in the early hours of the morning.
Police launched a homicide investigation soon after.
The young mum lived at the Maich Rd house with her parents and daughter.
She had been out to a friend's birthday party and it appears she was killed soon after she arrived home.
Her parents, Rakesh and Aradhana Singh, had also been out visiting relatives and found her body when they returned.
A source said that when her parents got home they found the main door unlocked.
"When they went in her room they found her on the floor in a pool of blood," the source said.
"She had injuries to her face and body."
A scene examination with specialist forensic staff continues today.
Police would like to hear from any members of the community who may have been in the Maich Rd area of Manurewa on Saturday night or Sunday morning.
Any witnesses should contact the Counties Manukau Police on 09 261 1321.
To pass information to police anonymously, they could call Crimestoppers on 0800 555 111.
It's understood a NZDF aircraft and multiple helicopters are involved.