A man has been arrested on suspicion of murdering 18-year-old Donnell Rhule in south London on Wednesday.
The 26-year-old was taken into custody on Friday evening, Scotland Yard said.
A post-mortem examination revealed Mr Rhule suffered a fatal wound to the chest, consistent with a knife.
The force said a “number of suspects and vehicles” were involved in the murder and appealed for witnesses. It said West Dulwich, where the stabbing happened, was “generally quiet”.
Homicide detectives from the Specialist Crime Command, who are leading the investigation, believe the Donnell was attacked on Lyall Avenue before making his way to a parade of shops on Seeley Drive.
‘Number of suspects’
Det Ch Insp Rob Pack, of the Met, said: “I would like to speak with anyone who witnessed the stabbing or who saw anyone leaving the scene.
“This is a generally quiet area, so I am certain that a number of people will have seen or heard something significant.
“Although one person has been arrested, we are still very much in the early stages of the investigation. We know a number of suspects and vehicles were involved in this murder and I’m appealing for help in identifying and tracing them.”
‘Increased policing presence’
Scotland Yard said the teenager’s next of kin have been informed.
Ch Supt Colin Wingrove, commander of the Met’s Central South Command Unit, said: “I am saddened to hear of this tragic murder and our thoughts are with Donnell’s family, friends and the wider community.
“Our local safer neighbourhood officers will provide an increased policing presence in the coming days to provide reassurance and support.”