Shakur Hassan, 23, died after being shot just yards from Hayes town centre at 10pm on October 13.
A 15-year-old girl was among the bystanders who tried to save his life.
Despite the efforts of emergency services, Mr Hassan was pronounced dead at the scene a short time later.
Police charged a 16-year-old boy with murder on Saturday.
He has been remanded in custody and will appear at Uxbridge Magistrates’ Court on Monday.
The Metropolitan Police said a 46-year-old man has been arrested on suspicion of murder and is currently in police custody.
Two men, aged 31 and 21, were arrested in connection with the incident. They were taken to a west London police station and subsequently released with no further action.
At the time of Mr Hassan's death, flowers, candles and balloons were left at the crime scene on Austin Road by friends and family. One card said: “RIP Bro forever in my head. The kindest soul fallen. Rest in eternal peace.”
Another said “sleep tight” and a third “Love you always.”