Denardo Samuels-Brooks was attacked on Prentis Road at around 4.15pm on Thursday.
He was taken to hospital but despite the best efforts of the emergency services he was pronounced dead at 4.51pm.
A post-mortem examination took place at Greenwich Mortuary on Saturday and gave cause of death as a stab wound.
The victim’s next of kin have been informed, police said.
Since the attack four teenagers have been charged with murder.
A 17-year-old boy and Umar Salami 18, have been remanded in custody and will appear the Old Bailey on Tuesday, June 15.
Denzel Kwatng, 19 and Andre Headley, 18 will appear at Wimbledon Magistrates’ Court on Monday, 14 June.
Two 16-year-old girls were arrested and have been bailed pending further enquiries.
Four other people – a 15-year-old male; a 16-year-old male; a 17-year-old female and an 18-year-old man have been released under investigation while enquiries continue.
Anyone with information that could assist the investigation is asked to contact police on 101 or tweet @MetCC and quote CAD 5897/10June. Alternatively, contact the independent charity Crimestoppers anonymously on 0800 555 111.