Witnesses said that a teacher from a nearby school shielded his pupils, aged 12 and 13, who had been playing rugby, before rushing over to help Mr Wali and giving him CPR.
He was taken to hospital but was pronounced dead around an hour later. His next of kin have been informed.
The scene of the attack is yards from Richmond upon Thames College, which confirmed on Wednesday that the victim was one of its students.
‘This loss is sure to raise many emotions, concerns and questions’
The college’s principal, Dr Jason Jones, said: “Our thoughts and prayers are with the student’s family and friends at this difficult time.
“This loss is sure to raise many emotions, concerns, and questions for our students, parents, staff and local community.”
In a statement, the college said it was cooperating with the police investigation as well as providing support and counselling to students and staff, and has boosted security and surveillance at its entrances.
A relative living in Stanmore, west London, told the Evening Standard: “Hazrat was a very good boy. He came here to study, he was living all on his own in London. His immediate family are all back in Afghanistan.
“I saw him in hospital. He had a fight is all that I’ve heard.”
Police working to establish motive
Detective Chief Inspector Vicky Tunstall, from the Met Police Specialist Crime Command, said: “The incident occurred in a playing field area and was witnessed by a number of people.
“Some of those people are believed to have filmed events as they unfolded; I ask that any videos are not shared via social media to avoid causing the young man’s family any more distress at this already incredibly difficult time for them.
“Instead, please go to the police immediately. A number of people have spoken to us, but we need to hear from anyone who has information that could help.
“We are still working to establish the motive behind this tragic attack and are following a number of leads.
“Officers have recovered CCTV from the area and spoken to a number of witnesses who described seeing a fight in the moments before Hazrat was attacked.
“We know a lot of people were on the field at the time and I’d urge anyone who has not yet spoken to police to contact us immediately.”