The Afghan national arrested over a triple stabbing in Uxbridge was granted asylum after arriving in the back of a lorry, the Daily Express understands.
The 22-year-old was Tasered and arrested after a man was stabbed to death and two other people, including a 14-year-old child, were injured in the incident on Midhurst Gardens.
The suspect arrived in the UK as an “unaccompanied asylum-seeking child” in 2020 and was granted leave to remain in 2022, it is understood.
Officials confirmed that the suspect does not live in an asylum hotel or any other form of Home Office accommodation.
A 49-year-old dog walker died after being treated at the scene, while another man, aged 45, suffered life-changing injuries. The 14-year-old boy's injuries were not life-threatening nor life-changing.
Detectives are trying to establish the relationship between the suspect and the three victims, but the attack is not being treated as terrorism.
The suspect, who allegedly lived as a lodger in the home of the 45-year-old, chased two victims out of the house after a fight broke out, locals said.
Witnesses claimed the 49-year-old man, who was walking his dog at the time, tried to intervene. They alleged he was then cut across the neck.
Logan Woolley, 16, who lives on Midhurst Gardens, was watching TV when he saw a person “running with a knife in his hand, covered in blood”.
“I saw him get tasered and another person getting CPR.”
He said he had seen the victim walking his dog in the mornings and evenings.
Footage posted online appears to show the suspect walking along a residential street, before two police officers sprint after him, one pointing a Taser and shouting “drop the knife” and “get on the floor”.
Several others join them before the Taser is fired and the man falls to the ground.
One witness told the Daily Mail: “The Afghan man was chasing a man and a boy around the road and a local man who was with his dog tried to stop it.
“There was blood everywhere and the paramedics were there for at least 30 minutes trying to save his life. It was absolute carnage and very distressing to see.”
Another local added: “The dead man is very well known around here. He's a lovely guy, very gentle and peaceful. He was just trying to help and it's ended up costing him his life.”
A third witness said: “I saw a young man come running out of the house waving a large knife around. He had a mad look in his eyes and was screaming.”
Chief Superintendent Jill Horsfall urged the public not to share the shocking footage of the attack online.
He said: “This was a shocking and senseless act of violence that has left one man dead and two others injured.
“Our thoughts are with the victim's family and friends at this unimaginably difficult time.
“The incident will have understandably caused concern to the local community. I have deployed multiple officers to the local area, they will be here throughout the week to provide reassurance while detectives work intensely to piece together the circumstances.
“I understand that there has been a lot of speculation online following on from this incident. We ask that you rely on us for information, and that you do not share sensitive footage.”
A Home Office spokesperson said: “Our thoughts are with the family and friends of those affected by this horrific incident.
“We are receiving regular updates from the Metropolitan Police. The priority must now be for the police to investigate so those responsible can be brought to justice.”