Detectives believe Alexander Kareem, 20, was killed in a case of mistaken identity on 8 June as he made his way to a shop in Shepherd’s Bush.
Five men, aged 18 to 24, a boy, 16, and a woman, 34, were arrested in the early hours and are in custody.
Mr Kareem’s sister Khafi Kareem, a Met Police officer, said her brother’s life had “mattered”. Mr Kareem had just been to a shop and was riding a scooter to a friend’s home when he was killed on Askew Road.
A white Range Rover, which had been seen speeding away from the crime scene, was later found burnt out.
Det Ch Insp Wayne Jolley said the arrests were a “significant development.”
“I believe this murder to have been a case of mistaken identity, perpetrated recklessly and with no regard whatsoever for human life.
“We will continue to work hard to make sure those responsible are brought to justice.”
Speaking at his funeral last week in Hammersmith, Mr Kareem’s family begged the public to not view his death as “just another black boy who’s been shot”.
Ms Kareem said her brother had planned to start university in September to study computer science.
She added: “To anybody who’s seen this [in the news] and is thinking this is just another black boy who’s been shot by violence, I want to tell you that is not the case.
“Alex’s life mattered, he had a future ahead of him, he’s not just another black boy. He had a family, he had friends, this is real.”