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.
Police at the scene of a homicide on Maich Road in Manurewa on Sunday morning. Photo / Jason Oxenham
"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.
