Four young men were arrested today over the carjack killing of Harjinder Singh Bhurji.
Three suspects - a 20-year-old, a 19-year-old and a 17-year-old - are being held at an east London police station after being arrested on suspicion of murder, Scotland Yard said. The fourth man is being held for handling stolen goods.
Relatives spoke today of their heartache at the death of the 32-year-old, who was apparently stabbed in the chest after refusing to hand over the keys to his black Mercedes CLK coupe.
Mr Bhurji - an unmarried garage owner - was sitting in his sports car talking to a female friend when the robber opened the passenger door and dragged the woman from the car.
The victim, who lived in Ilford, east London, initially tried to hide the car keys under his seat but the robber threatened to harm his friend if he did not hand them over.
He was stabbed as he attempted to retrieve the keys before the thief, who drove off with his vehicle.
Mr Bhurji's uncle, Narinder Shargill, who has flown from San Francisco to be with his relatives, expressed his shock over the "senseless" crime.
The victim's best friend Gurmit Birdi, 32, said Mr Bhurji's family was "distraught".
Mr Birdi, a British Airways cabin crew member, said Mr Bhurji had been due to act as best man at his wedding in India on November 1.
"He was a very nice person, he never did anything wrong. He lived his life and enjoyed his life, he was a happy person. He was just in the wrong place at the wrong time," Mr Birdi said.
"For his family and friends, this is just unbelievable. I can't even think straight, God knows what his family are going through."
Mr Shargill told ITV1's Daybreak: "My sister got married two weeks ago so the entire family was here from all over the world. It was a time of joy and celebration.
"Two weeks later to be in a state of mourning is just incredible. We just can't imagine something like this (would) happen. This crime is so senseless."
Mr Bhurji was pronounced dead at the scene in Stoneleigh Road, Ilford, after police were called at 1.10am yesterday.
The car, registration number R4 JXW, was found abandoned in Forest Glade, Chingford, east London, at 2.45am.
Mr Bhurji's friend who was with him at the time was found at the scene uninjured but suffering from shock.
Two ambulance crews were sent to the scene, along with a single responder in a car and a London air ambulance doctor in a car.
"Sadly, despite the best efforts of our staff, one person - a man - was pronounced dead at the scene," a spokesman for London Ambulance Service said.
Murder squad detectives are still keen to hear from anyone who saw the car, possibly driving at high speed, anywhere between Stoneleigh Road and Forest Glade, a journey of about three miles.
The thief may have travelled down the A406 North Circular Road or through main back roads.
Detective Chief Inspector Phil Rickells, who is leading the investigation, said: "The suspect appears to have been purely motivated by stealing the car because at this early stage we can find no other obvious motive.
"As far as we can tell, the victim did not know the suspect or why he might want his car.
"The Mercedes had a distinctive number plate and I would appeal to anyone who was out driving in the early hours to cast their minds back and let us know if they saw it."
A post-mortem examination was being held today at East Ham mortuary.
Anyone with information is asked to contact the incident room on 020 8345 1570 or Crimestoppers anonymously on 0800 555 111. No arrests have been made.