A 20-year-old man has been shot dead, police said.
Officers were called at 4.15am on Saturday morning to Waylett Place, West Norwood, south London, Scotland Yard said.
The victim was taken to hospital, suffering from gunshot wounds to the chest, and died at 5.33am, a Yard spokesman said.
Three males have been arrested in connection with the incident, and remain in custody, he added.
Next of kin have been informed, but formal identification has yet to take place, the Yard spokesman said later.
A post-mortem examination was due to take place at 6pm.
Detective Chief Inspector Caroline Goode from the Homicide and Serious Crime Command, leading the investigation, said: "At this early stage we believe there was an altercation between two groups of black men in the vicinity of the bus stop at Waylett Place and Norwood Road which has resulted in this man being killed.
"I would urge anyone who was in the area at the time, and who may have seen or heard anything suspicious, to come forward as you may hold significant information."
The three men who were arrested were held near the scene.
Anyone with information was asked to contact Crimestoppers on 0800 555111.