Evren Anil was sitting in the passenger seat of his sister's car when teenagers threw their litter through the window. Police say that when he got out of the car to confront the youths he was either stabbed or punched in the face and lost his life.
Evren Anil was 23 and had just graduated from university with a high grade. For having the bravery to challenge anti-social behaviour, he paid the ultimate price.
Witnesses to an attack on a graduate who was killed in a row over litter are refusing to come forward because of "misguided loyalty", police have said.
Detectives said people know the identity of the killer of Evren Anil, who died eight days after being punched by a youth who threw litter into a car.
The 23-year-old died on Tuesday after he was attacked in Crystal Palace, south-east London.
Five people have been bailed over the attack on 5 August.
Det Ch Insp Cliff Lyons said: "I know that there are witnesses who have not come forward and I know there are witnesses who are aware of their identity.
First class degree
"They have refused to come forward for ridiculous reasons - misguided loyalty, they do not want to be seen as a 'grass'."
Mr Anil, from Upper Norwood, south-east London, fell into a coma soon after hitting his head on the pavement during the attack.
He was in the front passenger seat when teenagers threw rubbish through an open window of his sister's car as they waited at traffic lights on Central Hill.
Police said an elderly passer-by intervened when the youths produced a knife, but that person left the scene when the blade was put to his throat.
The passer-by then alerted the emergency services.
Both suspects, who were described as being black and in their late teens, ran off into the nearby Central Hill Estate.
Mr Anil had recently graduated with a first class degree in computer science from Kingston University.
BBC / Worldbulletin