In October 2020, George Makia, now 18, fatally stabbed Bubacar Jabbie Dukureh in the chest just metres from his home.
An earlier trial found four others guilty of his murder.
On the evening of October 23, 2020, the victim, known as Buba, was stabbed in the chest and collapsed on his doorstep in a pool of blood after being attacked by five teenagers.
Samuel Bartley, 19, Jamal Dakissaga-Benitez, 19, Alfie Ferguson, 19, and Kaiyan Decordova, 20, were found guilty of murder in a previous trial.
Makia, who was 15 at the time, was not present at the trial because his family had taken him abroad and he had only returned to the UK a week before it began.
In the hunt for the killer of their son in the 2018 Walthamstow attack, the family has offered a £50,000 reward.
The defendant from Walthamstow, who has been identified since the age of 18, denied any involvement but was convicted of murder in January.
Baba’s “devastated” parents and siblings described him as a loving, friendly, popular, and quiet young man in victim impact statements.
His mother, Haja Dukureh, said the “vile killers” not only took Baba’s life but also ruined his family’s by their “evil barbaric” actions.
“We hope and pray for justice for Baba,” she said.
“We opened our front door and saw our little brother lying in his blood,” his brothers said. We will remember seeing him like this – our brother lying in his blood.
“This has had a huge impact on our lives and we are still grieving for what has happened to Baba.”
Makia was sentenced to life in prison with a minimum term of 15 years by Judge Anuja Dhir KC on Friday.
“Having heard the evidence at both trials, I am certain that this was a professional, coordinated, planned ride-out – that was clear from your actions before, during, and after the killing,” she told Makia.
“Bubacar Dukureh was not the intended target; he was simply present. And you, along with the others in your group, murdered him. Your victim had no defence and was unarmed.
In my opinion, it is clear that you were all working together. You were acting in concert and as a team, whoever was carrying the knife or knives.”
Prosecutor James Dawes KC previously described how the attackers were identified on CCTV, with two on bicycles and three on foot.
The attackers were members of the Higham Hill or Priory Court Boys gang, which competed with the Drive Marlowe and St James or Mali Boys gangs.
“It’s the Crown’s case that Buba had the appearance of a Mali Boy for them, and that was enough to get him killed,” Mr Dawes said.
Jurors were shown a video clip set to a drill rap that was discovered on the defendant Ferguson’s phone and focused on the victim’s address.
According to Mr. Dawes, the video appeared to be “glorifying” the murder and was intended to be posted on the internet.
In mitigation, it was stated that Makia had no involvement in the creation of the video by Ferguson.
The judge agreed that Ferguson inflicted the fatal 12cm-deep wound and that, despite being armed, Makia did not draw his knife.
