A voice was apparently heard pleading for mercy before a young mother was kidnapped from her home and killed.
Kirsty Treloar, 20, was abducted shortly after 7am yesterday and was found dead in an abandoned car some 90 minutes later.
Neighbours said they heard a "hysterical" scream come from the property and a cry of "Please, please, please" before Ms Treloar was taken away.
Her body was discovered with stab wounds at around 8.30am in a grey Fiat Stilo which was abandoned about a mile from her home in Hackney, east London.
She was pronounced dead at the scene in Ryder Mews.
It is understood police believe it to be a domestic incident.
A 22-year-old man and a 24-year-old woman - believed to be Ms Treloar's siblings and named in reports as Dean and Gemma - were also injured in the attack and were treated for stab wounds.
Today the man remained in an east London hospital in a "stable" condition.
A month-old baby girl was also taken to hospital as a precaution.
Yesterday neighbours expressed disbelief as forensics officers examined both scenes which were cordoned off with police tape.
A tarpaulin covered one of the ground-floor windows of Ms Treloar's home in Brownlow Road.
One neighbour, who asked not to be named, said he heard what sounded like a window breaking early this morning and a person shouting "Please, please, please".
Another woman living close to the three-storey property described how she was woken at around 5.30am before hearing "a female sounding extremely distressed".
The woman, 45, who did not want to be identified, added: "I thought it might be foxes fighting, which can sound quite human.
"Then I thought, 'No, it's definitely not', it sounded like a young woman in distress. It was very short-lived and stopped quite abruptly.
"It sounded like she was a bit hysterical."
Terry Tundervary, 58, a builder living on the same leafy residential road, said the family - named locally as mother Pamela, and siblings Gemma, Dean and Jade - was "very friendly" and would often stop to "say hello" when they met on the street.
A man believed to be Ms Treloar's stepfather is understood to live at the same address. Neighbours said he was employed by Hackney Council.
Speaking of Kirsty, Mr Tundervary said: "She was a pretty girl, a very normal girl".
Retired couple Mary and David Ward, both in their 70s, also spoke of their shock.
Mr Ward, 70, said: "We couldn't believe all this happened, it's a real tragedy.
"The area is pretty good really, we've lived here nearly 30 years and it's the first time anything like this has occurred.
"We have never had any trouble - we didn't know the family but the young girl seemed to be very nice when we saw her to say hello to."
Scotland Yard have not made any arrests.
Police said "extensive" inquiries were being carried out to trace the suspect.
A post-mortem examination for Ms Treloar will take place in due course.
A spokesman for the force said: "Whilst we await formal identification we believe the victim to be Kirsty Treloar."
Tributes were left on a Facebook page set up in Ms Treloar's name.
One posting, from Kerry Louise Clayden, read: "RIP kirsty my thoughts are with ya family and your baby girl xx".