Rijkaard Salu Siafa was pronounced dead at the scene in Fellmongers Yard, Croydon, after officers were called just after 6pm on Friday.
One man was arrested and remains in custody.
Met officers, paramedics, and London’s Air Ambulance all attended the scene. Photos showed a huge emergency response, including least six police cars.
A crime scene was in place on Friday night and police officers were carrying out urgent inquiries in the area.
Detective Chief Inspector Sarah Lee, from the Met’s Specialist Crime Command who leads the investigation, said: “Our thoughts and deepest condolences are with Rijkaard’s family and friends who are coming to terms with his death following this shocking incident. This loss has ripped an irreparable hole in their family and I would ask their privacy is respected at this difficult time.
“I would also like to thank those members of the public who rushed help Rijkaard in the immediate aftermath.
“If you saw events unfold but have yet to contact police, then I would ask you do so immediately.
“Local residents will continue to see an increased police presence around the area of Fellmongers Yard – if you have any concerns, please speak to one of them.”
Superintendent Mitch Carr, who leads for community policing in Croydon said: "First and foremost our thoughts are with the family and friends of Rijkaard who has lost his life in tragic circumstances.
"The local teams in Croydon will be working to ensure a visible police presence across the Town Centre to offer reassurance to the community. Please do speak to officers about any concerns you may have.
"I would also like to pass on my thanks to the community for their assistance and cooperation to officers who responded to this extremely challenging incident."
Anyone with information is asked to call 101 or ‘X’ @MetCC and quote CAD6022/12Apr. You can also provide information anonymously to the independent charity Crimestoppers on 0800 555 111.
