The mother of Jamil Palmer, the teenager killed after being stabbed on Tuesday, said the pain caused by losing her son was unimaginable, as she made a tearful plea for witnesses.
Ashifa Sayani begged anyone who may know what happened to her 18-year-old son to come forward.
Mr Palmer died after a being stabbed near Evans Grove, Feltham at 3.30pm on May 6. Two people were arrested and released on police bail until the middle of this month.
She said: "We have lost our beloved Jamil.
"Do the right thing in Jamil's memory. Forget your street code, it is not grassing and it is not cool. Just tell the police what happened and who was involved.
"I've lost my son. The hurt that has been caused is unimaginable.
"All I ask is that you trust the police and come forward. How would you feel if this happened to your loved one?"
"You have all shown great love, with the flowers and gifts left at the bench, please don't let him down, you were all there with him through life, be there through death, stand by him, your mate, help him rest in peace."
The Kingston College student, from Hampton, was airlifted to hospital where he later died.
A postmortem examination has not yet taken place.
The investigation is being led by detectives from the Homicide and Major Crime Command under Detective Chief Inspector Noel McHugh.
DCI Noel McHugh said: “I believe there may be a number of persons in the community who may hold vital information about Jamil's murder and are yet to come forward and speak to the police.
“Whatever their reasons for not coming forward so far, I would like to take this opportunity to reassure anyone worried about speaking to officer that they will be treated with the utmost sensitivity."
An 18-year-old man and 16-year-old man were arrested on suspicion of murder on the day of the death and have both been bailed to return to police in mid-May.
Anyone with information should call the incident room on 020 8785 8099 or Crimestoppers anonymously on 0800 555 111.