Kieron Charles, 17, was one of two boys to be stabbed in Erconwald Street soon after 1pm yesterday (April 5).
The emergency services rushed to the junction with Du Cane Road and Old Oak Common Lane, a small shopping area among houses.
Kieron, from East Acton, died at the scene despite the attempts to save him by paramedics.
The second teenager, aged 16, was taken to hospital with stab wounds that are not life-changing and then discharged.
Soon afterwards a teenager, 16, was arrested on suspicion of murder and put into custody where he remains.
Early this morning (April 6) a third teenager, also 16, who left the scene after the incident was tracked down and arrested – they are also in custody.
Detective Chief Inspector Alex Gammampila is leading the investigation.
He said: “This is an awful incident in which a teenager has lost his life.
“The thoughts of everyone in the Met remain with Keiron’s family and loved ones as they begin to come to terms with their tragic loss.
“Detectives have worked around the clock to follow every possible available line of enquiry and I’m pleased that we have made two arrests as part of our early enquiries.
“While we are working hard to understand the exact circumstances, we are not looking for anyone else in connection with this incident at this stage.
“I’d like to appeal directly to anyone who was in the area between 1pm and 1.20pm on Saturday and witnessed the incident.
“Our team are also keen to speak to anyone who might have any other information that might assist us.
“Keiron had his whole life ahead of him and any information might prove vital in achieving justice on behalf of his family.”
Police are asking anyone with any information at all to come forward.
A spokesperson added: “Do you have CCTV or phone or dashcam footage?
“Have you been sent footage of the incident or seen anything that might be able to help detectives on social media?
“If so, please get in touch with police, or Crimestoppers, as soon as possible.
“Anybody who witnessed the incident – or who has any information which can assist with the investigation – should contact the police officers on 0207 175 2206, quoting reference 3435/05APR.
“Alternatively you can provide information, and upload any footage directly to the investigation team by using our Major Incident Public Portal: https://mipp.police.uk/operation/01MPS25X56-PO1
“You can remain 100 per cent anonymous and pass information onto the independent charity Crimestoppers on 0800 555 111 or by visiting Crimestoppers-uk.org”
