Paramedics from London Ambulance Service and London’s Air Ambulance battled to save his life for 45 minutes but he was pronounced dead at the scene.
Two men, aged 18 and 21, and a 17-year-old boy have been arrested on suspicion of murder.
They are being held by police for questioning.
A Metropolitan Police spokesman said: “Next of kin have been informed, but officers await formal identification.
“Detectives from the Homicide and Major Crime Command are investigating.”