Police were called at 9.10pm on Tuesday, 30 March to reports of three men fighting in Alpha Road, Croydon.
Officers attended and found a man who had been stabbed. Paramedics also attended but despite the best efforts of the emergency services, the man was pronounced dead at the scene.
Detectives are confident the man is 23-year-old Reece Young. His family have been informed and are being supported by specialist officers.
Two men had left the scene in a vehicle before police arrived. They later presented themselves at a south London hospital with stab wounds that are believed to have been sustained in the same incident.
Officers attended the hospital and arrested both men on suspicion of murder.
The first, [A], aged 33, remains in hospital where he is being treated for non-life threatening injuries.
After his arrest, the second man, [B], believed to be in his 30s, assaulted police officers and NHS staff before forcing his way out of the hospital. Urgent enquiries are ongoing to trace him.
An investigation has been launched by homicide detectives from the Met’s Specialist Crime Command.
Detective Chief Inspector Richard Vandenbergh, who is leading the investigation, said: “We believe this incident was witnessed by a number of people. They had gathered for a small vigil in remembrance of another recent fatal stabbing victim when an altercation began.
“Some of those people have already spoken to police, but I believe there are others who captured images and video of what happened. I need those people to contact us immediately. The information they have could prove vital in establishing the chain of events that has led to a young man losing his life.
“One arrest has been made and my team are working with colleagues across the Met to establish the whereabouts of the second man. We believe he suffered injuries that require urgent medical attention. He is urged to make contact with us immediately.”
A crime scene remains in place and enquiries into the circumstances are ongoing.
Any members of the public with video or images that could assist police can upload footage here.
Anybody with information is asked to call police on 101 or tweet @MetCC quoting CAD 7449/30MAR.
Information can also be provided to Crimestoppers, anonymously, by calling 0800 555 111.