The incident happened in Midhurst Gardens, Uxbridge at around 5pm yesterday (October 27).
Officers and London Ambulance Service crews attended and found three people who were stabbed.
One man was pronouncded dead at the scene.
His next-of-kin have been informed and are being supported by specially-trained officers.
A 45-year-old man and a 14-year-old boy were also treated at the scene before being taken to hospital.
The man’s injuries were confirmed to be life-changing and the boy’s condition was non-life threatening.
A 22-year-old man was arrested at the scene on suspicion of murder and attempted murder.
He was hospitalised as a precaution after officers deployed a Taser.
He was not injured and has since been taken into police custody.
An investigation has been launched and urgent enquiries remain on-going.
Anyone with information is urged to call 101, quoting crime reference 5129/27OCT.
Alternatively you can call Crimestoppers on 0800 555 111 to remain anonymous.
This is a breaking news story. More to follow.
