The Metropolitan Police have launched an urgent appeal to track down a 16-year-old boy who is wanted on suspicion of murder.
George David, 16, from Downham, south-east London, is a suspect in the killing of 21-year-old Gabriel Petrov Stoyanov.
Police say David has links to Bromley and Orpington.
A murder investigation was launched after Mr Stoyanov was stabbed in Bromley Road, Downham following an incident shortly before midnight on Friday November 4.
George David
Metropolitan Police
Police officers arrived at the scene along with their colleagues from the London Ambulance Service.
The emergency services found that Mr Stoyanov had suffered a stab injury and transferred him to hospital.
He died of his injuries on the afternoon of November 5.
A 14-year-old boy and a 17-year-old man have already been arrested on suspicion of murder and remain in custody.
Detective Chief Inspector Kelly Allen said: "Two arrests have been made as part of our investigation, but we urgently need to speak to George David.
“Officers from across the Met are working to trace him.
"George, my message directly to you is that you must attend a police station immediately.
"We believe it's possible George is being hidden or moved around by people he knows.
“My message to those people is that if you are working to frustrate our enquiries you should be very much aware of the trouble you could find yourself in.
“We will seek to arrest and prosecute you to the fullest extent of the law.”
The Met said: “Anyone who sees him is urged to call 999 immediately, reference CAD 8645/4 Nov. He should not be approached by members of the public.
“Information as to his whereabouts can be given to 101 or tweeted @MetCC using the same reference.”