Junior Jah was found with knife wounds two weeks before he was fatally stabbed and shot in Custom House.
Abubakkar Jah - also known as Junior - died after being wounded in Coolfin Road on April 26.
But the Recorder can reveal that the 18-year-old was found with stab injuries two weeks before his death.
Officers had been called to reports of a fight in Prince Regent Lane, Custom House, on April 9 at 4.26pm.
They attended and during a search, found Junior and a 19-year-old man in Sark Walk.
A Met spokesperson said: "They were taken to hospital by paramedics where their injuries were not life threatening."
She added that both victims had decided not to support an allegation.
Enquiries led to the arrest of a 29-year-old man on suspicion of grievous bodily harm with intent. However, he was released with no further action.
When all potential lines of enquiry had been explored by police, the case was shelved for review, pending new evidence coming to light.
At a meeting to discuss community safety following the deaths of Junior and Fares Maatou, resident Mohammad Uddin asked what happened when a young person is under threat.
He said: "It was just really strange for me and others to hear that [Junior] was let back into the community straight after he was attacked, even though he was vulnerable."
Mr Uddin asked: "What is being done to coordinate a response if something happens, if there is a threat or intelligence of an incident? How can people be taken out of situations which may be harmful for them?"
Tim Aldridge, corporate director of children's services at Newham Council and statutory lead on safeguarding, said: "That is something we will need to review as part of our learning into what happened and how we might prevent similar tragic incidents happening again in the future."
He explained the town hall can work with families to reduce risks to young people, including by relocating them or using legal powers to protect under 18s.
But the response depends on evidence and the level of risk put forward by different agencies.
A "partnership response" is being developed by the town hall with a pathway for young people who are at risk improving "month by month", the meeting on Monday, May 17 heard.
"We absolutely recognise we don't always get it right and when tragic incidents happen, we are absolutely there to learn from what went wrong. We take every step possible to try and avoid the same mistakes happening again," Mr Aldridge said.
He echoed a point raised by borough commander Richard Tucker - who was also at the meeting - that the system is "very complex".
Keisha McLeod, mother of Corey Junior Davis who was killed in 2017, said the deaths of Junior and Fares made it feel as if she had lost her son all over again.
Ms McLeod said children in Newham have an embedded fear and distrust towards services.
"We need a different way of dealing with the situation from early on," she added.
Annu Mayor, a member of the borough's youth safety board, said young people had reported not trusting the police, preventing them from coming forward.
Mr Tucker replied: "I can understand why people don't get on with police because we are the enforcers.
"People going around killing people? There should be such a robust response. If you know something, you've got a duty as a citizen to tell the police.
"When all these children say they don't trust the police, do we challenge them? Why not? It's too easy to criticise."
Paul Leslie, who chairs Newham's independent advisory group which challenges police practices, called for "robust" action by law enforcement, coupled with "robust" opportunities for youngsters.
Mayor of Newham Rokhsana Fiaz described the devastation young people feel.
"Everyone has to step in and step up," Ms Fiaz said. "Together, united in our anger, in our pain, but in our collective focus and commitment to dealing with this and getting to the root causes, we will prevail."
On Tuesday, May 18, detectives investigating Junior's death arrested five people for conspiracy to commit murder. A 30-year-old woman arrested on May 2 has been released under investigation.
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