The boy was treated by paramedics on Westbourne Road near the junction of Sheringham Road at 1.02pm today (December 9).
He was rushed to hospital, however, died shortly later during the afternoon.
His next-of-kin have been informed and are being supported by specialist officers.
A crime scene remains in place on Atlas Mews, Westbourne Road and Arundel Square.
A Metropolitan Police spokesperson said: “We understand this is incredibly concerning for the community, particularly considering the young age of the victim.”
Anyone who has information that may help police with their investigation is asked to contact police on 101 quoting ref CAD 3568/09DEC.
Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
