Police were called at 4.24pm on Tuesday, June 8 to reports of shots fired in Hornsey Rise Gardens, in north London.
Officers attended the scene along with London Ambulance Service and London’s Air Ambulance.
They found 19-year-old Cox, who is from Barnet, suffering gunshot injuries.
He was taken to hospital where he was later pronounced dead.
A post-mortem examination gave cause of death as a gunshot wound to the head.
An investigation was launched by the Met which is being led by detectives from Specialist Crime (Homicide).
On Saturday, June, 12, a 19-year-old man was arrested on suspicion of murder. He has been taken to a London police station where he remains in custody.
Enquiries continue. Anyone with information is asked to call 101 or tweet @MetCC quoting Op TREWEN and CAD 5570/08JUN21.