Ethan Nedd-Bruce, 18, was gunned down outside Collins House in Armitage Road, Greenwich, on 22 October 2018.
His killing has devastated his family and friends who, two years on, are still searching for the truth about what happened and for those responsible to be brought to justice.
On the night of his murder, which happened at around 9.25pm, Ethan had been involved in an altercation with a group of men minutes earlier in Woolwich Road. As Ethan fled, the males pursued him into Armitage Road on a motorbike, and in a silver Ford Kuga car, where he was attacked and killed.
Detectives are offering a £20,000 reward for anyone who provides information which identifies those responsible.
Detective Chief Inspector Richard Leonard, from the Specialist Crime Command, leads the investigation and said: “It is now two years since Ethan was murdered but we have not given up. We know Ethan was attacked as he left a chicken restaurant in Woolwich Road at around 21:20hrs that evening.
“We have an image which shows someone we believe could be a key witness; a white male with a beard holding a mobile phone. We believe he walked past the chicken shop where Ethan was shortly before the first attack.
“This person – who I want to stress is not a suspect – may well have seen something that could assist with our investigation and I would urge him to make contact with officers.
“We are also releasing footage showing the two vehicles Ethan’s attackers used that evening. One is a motorbike with a rider and pillion passenger; the other is a silver Ford Kuga with a number of occupants.
“Both these vehicles were in Woolwich Road at the time of the first altercation and then pursued Ethan into Armitage Road.”
CCTV footage shows his attackers arriving in Woolwich Road, apparently clear in the knowledge that Ethan was inside the restaurant.
Detectives believe Ethan’s murder was a targeted attack linked to a number of other incidents in the area between two criminal groups but officers are confident that the organised crime gang has since been largely dismantled.
DCI Leonard added: “It’s not too late to do the right thing.
“Someone out there knows who did this,” he said. “It is not too late to do the right thing and speak to us about what you know. Help bring some closure to Ethan’s family who have been left utterly heartbroken by his death.
“Whatever the motive in this case, Ethan did not deserve to be pursued and attacked in this brutal and shocking manner.
“I believe the answer to who is responsible for this attack lies within the local community and I would urge anyone with information to come forward and speak to my team or, if you are apprehensive about speaking to officers, then through the independent charity Crimestoppers which is 100% anonymous.
“Ethan’s death has left his family in pieces and they can only begin to heal once those responsible have been convicted. Please, do the right thing.”
Anyone with information should contact the incident room on 0208 721 4622