Police were called at 4:44pm on Tuesday, October 3, to reports of a stabbing at Coldharbour Lane, Brixton.
Despite the best efforts from officers and London Ambulance Service, the 22-year-old man died at the scene.
Later that evening, a 23-year-old man was arrested on suspicion of murder after attending a hospital.
Detective Inspector Kevin Martin, Specialist Crime, urged anyone with any information to come forward.
He said: “This awful attack took place in broad daylight, in front of people simply going about their business.
“I don’t underestimate the impact such a horrific incident will have had on anyone who saw it.
“I am also fully aware that there are a number of videos circulating following the incident, including of the crime scene.
“These videos are causing enormous distress for the loved ones of the victim, and I would ask people to respect them by not circulating this upsetting footage.”
Superintendent Gabriel Cameron, Central South Command Unit, announced that enhanced patrols will be seen in the area whilst Specialist Crime is investigating.
He said: “A young man has lost his life on our streets and the sense of shock is felt across the community.”
Any information, call 101 or post via @MetCC ref CAD 5530/3 Oct.
To remain anonymous, contact Crimestoppers on 0800 555 111.