Nisha Patel-Nasri had "loved" being a part-time police officer, said Fadi Nasri. "I was very proud of her," he said. "No one else could touch her."
Mr Nasri, 32, who ran a limousine rental business with his wife, was speaking as police appealed for a young couple to come forward. They may have seen the chief suspect running from the murder scene in Wembley, north London, just before midnight on Thursday.
The hooded man is suspected of trying to break into two expensive cars parked outside the couple's home - a stretch limousine and a Humvee all-terrain vehicle - when he was confronted by Mrs Patel-Nasri.
Detectives believe that Mrs Patel-Nasri's attacker, who police believe may also have been injured during the incident, could have been covered in blood after fatally stabbing her in the groin.
Mrs Patel-Nasri, 29, was an extremely popular local hairdresser and had been looking forward to attending the wedding today of her older brother, Katen Patel, 33. The civil ceremony has now been cancelled.
"She was so excited about it and had practically organised my side of the wedding," Mr Patel said. "Nisha will be hugely missed by everyone who knew her, especially by Fadi and myself. Things will never ever be the same."
He added that his sister "loved to help other people ... She was always talking about her police experience and wasn't frightened of anyone."
Police are investigating a possible link between Thursday's incident and an attempted burglary at her home last Saturday, when three men allegedly tried to break into her house. They fled after she challenged them on the porch of the suburban semi-detached house.
On Thursday night, the couple's neighbours on Sudbury Avenue, Wembley, were alerted after hearing screams.
They found the special constable in a nightdress, clutching her body. She was heard saying: "Somebody stabbed me, please call the police" before collapsing on the pavement. She later died in hospital.
Forensic search teams and detectives were combing local gardens and nearby wasteland and woods yesterday, as police tape, "murder appeal" posters and yellow police boards were put up on the street.
A chain of bouquets, including a large bunch of red roses, were lined up along the outside wall of the couple's home.
The part-time constable's murder has come as rank-and-file police officers intensify their demands to be armed with stun guns after a rise in violent assaults against them, including the murder last year of the police officer Sharon Beshenivsky.
PC Beshenivsky, 38, was shot dead during a raid on a travel agent's shop in Bradford, while her colleague, PC Teresa Milburn, 37, was seriously injured in the same incident.
The Police Federation is expected to release a poll this week showing that more than 23,000 officers, from constables to chief inspectors, want to be equipped with the devices known as Tasers.
Only trained firearms officers are currently cleared to use the weapons, which deliver a 50,000-volt shock.
At this week's annual conference, the federation will call for the so-called non-lethal weapons to be issued routinely to all officers, even though only 32 out of 51 British forces currently use them.
Mr Nasri said the couple, who had celebrated their third wedding anniversary on the day of her murder, had been looking forward to starting a family.
"Nisha was always helpful and always so forgiving. If she was angry she would be angry for two or three minutes and then it was over. She was extremely hard working, bubbly and always on the go," he said.
"She had been a special constable for about three years and she loved it. I was very proud of her and when she said she wanted to do it I encouraged her, but I had my worries for her safety.
"When she dressed up to go to work as a special she would ask me 'Do I look cute?' She was proud to wear the uniform."
Mr Nasri said that if one of his sister's customers had a birthday "she would cut her hair free of charge and that's typical of her generous nature. She was all about helping others."
THE CASE FOR TASERS...
Compressed nitrogen blasts out two electrified barbs up to a distance of 4.5 metres. The barbs attach to the suspect and can penetrate two inches of clothing. A 50,000-volt charge is delivered via wires connecting the barbs to the gun. Electric shocks induce muscle spasm and immediate paralysis without stopping the heart. The victim collapses to the ground.Reuse content