The 17-year-old victim, named by family members as Youssef Karim Hasan Al-Bayjani, was attacked by a gang at 2pm on busy Edgware Road yesterday lunchtime.
Mr Hasan Al-Bayjani, who was studying business at the City of Westminster College was found on the street suffering with stab injuries.
CCTV from a KFC diner showed a young man lunge at several hooded thugs before being set on on the pavement outside.
The victim was taken to hospital where he died five-and-a-half hours later. He had a brother and sister and lived nearby with his Kurdish mother.
A witness who saw the attack from Domino’s Pizza next door told the Standard that the teenage victim’s brother lay over him to try to protect him as he lay bleeding.
His brother was shouting telling people to get away. He was shouting ‘Get off, get off, he’s my brother’ and then the paramedics were there very quickly.’
A friend who left flowers at the scene said: ‘He had a really good heart. ‘On the day some boys were trying to mess with me, he stopped them and that was just about half an hour before it happened.
‘We’re just praying that this has to stop.
Floral tributes were left close to the KFC Shop in the Edgware Road after the 17-year-old was stabbed to death