The family of an off-duty special constable stabbed to death outside her home have made a public appeal for information to help catch her killer.
Nisha Patel-Nasri, 29, was found on the doorstep of her north-west London home just before midnight on Thursday.
Her husband Fadi Nasri said someone "has to know something" while brother Katen Patel made a direct appeal to the killer to give themselves up.
Police also want to speak to a second man and a couple who were in the area.
Mrs Nasri was attacked shortly before midnight after she went outside in her night clothes.
Police believe that she may have been investigating a noise outside her house in Sudbury Avenue, Wembley.
Her husband runs a limousine firm from the property, while his wife worked as a hairdresser.
"Obviously, someone has got a guilty conscience; they shall be worrying about what they have done, or be shocked; or maybe it was an accident or mistake, or whatever," he said.
He said his wife was devoted to her work as a voluntary police officer.
Police have asked people who may have seen a man, said to be wearing a hooded top, run from Sudbury Avenue towards Harrow Road.
They have said they are trying to trace a couple who may have seen the man and are trying also to trace a second man spotted walking "calmly away from the scene" in the opposite direction.
Mrs Patel-Nasri was stabbed outside her home
"Everybody's attention may have been drawn to the man running away instead of the man walking away," said Det Supt Julian Worker
"He may not have been involved but I definitely need that person to come forward."
Police are also looking at whether there was a link between the stabbing and an attempted burglary at the property on 6 May.
Mrs Nasri's brother, Katen Patel, said: "We want somebody to come forward, the person who did it - you as well.
"Please come forward and just admit it, because Nisha didn't deserve this. I don't want anybody to go through what Fadi and myself are going through at the moment, because it's so hard."
The 33-year-old, who was due to marry on Sunday, has now cancelled the ceremony.
He said his sister had been "so excited" about the event but "the day's here now, and she's not around, and I'm not even thinking about the wedding.
"I'm just thinking about her."
Earlier on Sunday, police officers held a minute's silence outside the house, where a number of floral tributes have been placed.
Mr Nasri said: "It does help, I'm touched, and I'm sure Nisha would be very proud of how the whole police have been - absolutely fantastic."