Yeray Sanchez-Morales was among two boys found injured in Old Kent Road, Bermondsey just before 10.50pm on August 27.
Officers attended and the pair were taken to hospital where Yeray died on September 3.
The second victim was taken to hospital where his injuries were deemed non life-changing or threatening.
He has since been discharged.
Shortly after the incident a 17-year-old boy was arrested by officers on suspicion of attempted murder.
He was taken into custody and later released on bail while enquiries continue.
On Monday, 1 September a 15-year-old boy was also arrested on suspicion of attempted murder.
He was charged with murder, grievous bodily harm and possession of an offensive weapon this morning (September 4).
He will appear this afternoon at Bromley Magistrates’ Court and cannot be named for legal reasons.
Detective Chief Inspector Kate Blackburn, of Specialist Crime South, who is leading the investigation, said: “Our thoughts are with Yeray’s family at this unimaginably difficult time. They are being supported by specialist officers.
“The incident took place in the middle of the road outside the McDonalds on Old Kent Road and there were many witnesses.
“Were you in the area at the time of the stabbing? Were you driving and have dash cam footage of the Old Kent Road? Did you witness the incident?
“If you have any information that could help police we urge you to call 101 quoting CAD 8387/27AUG. If you wish to remain anonymous, please speak with Crimestoppers on 0800 555 111.”
