Detectives are offering a £20,000 for information leading to the conviction of the killers of Trevor Ellis, who was shot in the head following a car chase as looters rioted through Croydon last year.
Mr Ellis, from Brixton Hill, was found with a gunshot wound to the head in a vehicle in Duppas Hill Road and pronounced dead at St George's Hospital the following day.
The 26-year-old and friends became embroiled in a disagreement with a group of around nine people involved in the disorder, officers said.
Detective Chief Inspector Chris Le Pere said: "Trevor Ellis was murdered a year ago on a night where Croydon, and in fact London, saw unprecedented levels of violence and disorder.
"I believe his killers were actively involved in looting and responsible for robbing at least two people that night. They thought nothing of arming themselves with a gun and ultimately taking a young man's life, leaving four young children without a father. I want anyone who was in central Croydon that night who saw this group or may have images of them on their cameras or phones to come forward."
The Met said the reward would be given for information that leads to “the identification, arrest and prosecution of the persons responsible for the murder”.
Detectives appealed for anyone who witnessed the car chase, which involved a dark estate car and a silver hatchback - believed to have been driven by the group - and a dark hatchback in which Mr Ellis was a passenger.
A number of people have been arrested in connection with the murder. Four men were released without further action, 10 are still on bail. Anyone with information should call police on 020 8247 4553 on Crimestoppers anonymously on 0800 555111.