Officers have launched a manhunt for a teenager who is suspected of stabbing a man to death with two other young people.
George David, 16, is wanted by the Metropolitan Police in connection with the murder of Gabriel Petrov Stoyanov, 21, in Downham, south-east London, last week.
The manhunt comes after two other suspects, aged 17 and 14, were arrested on suspicion of murder earlier this week.
Investigators believe David is being “hidden or moved” by people he knows as the probe continues.
Police warned anyone working against their efforts to locate the teen that they could be arrested and prosecuted.
A murder investigation was launched after Gabriel was stabbed in Bromley Road following an incident shortly before midnight on Friday, November 4.
Met Police officers and London Ambulance Service paramedics attended the scene and found the victim with a stab injury.
He was taken to hospital for treatment but died during the afternoon of Saturday, November 5.
A 17-year-old man was arrested yesterday on suspicion of murder and remains in custody at a south London police station.
A 14-year-old boy who was arrested on Tuesday, November 8 on suspicion of murder remains in custody after a warrant for further detention was authorised.
Detective Chief Inspector Kelly Allen, investigating, 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.”
Detective Chief Inspector Allen added: “This arrest shows the progress our investigation is making but there is still work to be done.
“One suspect remains outstanding and my team continues to pursue lines of enquiry to ensure they will be arrested.
“My message to that individual is clear – you know who you are and what you have done, and I would advise you to attend a police station at the earliest possible time before police find you.
“I would also continue to ask anyone with information that could assist us in our enquiry to come forward immediately.”
Anyone who sees David has been urged not to approach him and call 999 immediately, with reference CAD 8645/4 Nov.
Information as to his whereabouts can be given to 101 or tweeted @MetCC using the same reference.