A man has been stabbed to death at a vigil being held to remember the victim of another knife attack.
The Met Police said 23-year-old Reece Young was killed on Alpha Road in Croydon at about 21:10 BST on Tuesday.
Two men who later arrived at a hospital with stab wounds were subsequently arrested on suspicion of murder.
One of them attacked officers and NHS staff before forcing his way out of the building, but was later caught and returned to custody.
'Could prove vital'
Appealing for information, Det Ch Insp Richard Vandenberghhe said Mr Young had been found by officers responding to reports of three men fighting and it was believed the stabbing had been "witnessed by a number of people".
He said: "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.
"The information they have could prove vital in establishing the chain of events that has led to a young man losing his life."
Mr Young's family have been informed and are being supported by specialist officers.