Police said they believed he was attacked in Tulse Hill by a number of suspects.
The victim was found unconscious in the street on Monday and, despite the efforts of paramedics, was pronounced dead shortly before midnight.
Witness Paulina Wedderburn said the teenager’s mother and father were at the scene.
“The boy was laying down. He looked like an angel, like he was sleeping,” Mrs Wedderburn told reporters the morning after the stabbing.
“I just feel sorry for the mum. The mum’s screams, I can’t get out of my head.”
One of the boy’s friends, who had dinner with him on the evening he died, said: “He was bubbly. He was the friendly type. He was respectful. He had manners.”
Friends also said he was an aspiring rapper who was associated with the LTH (Lower Tulse Hill) gang and went to school at Park Campus in West Norwood.
A post-mortem confirmed the cause of death as a stab wound, but police are also investigating whether a gun was fired.
Another friend, who lives on the estate, claimed it took 20 minutes for emergency crews to arrive.
“I lost a friend,” he said. “If they had come sooner my friend would still be alive.”
Police have appealed for witnesses – or anyone with pictures or video of the scene – to come forward.
London’s mayor, Sadiq Khan, said this week that it could take a generation to the change the knife culture among some people in the capital