A teenager killed in a row over a mobile phone may have been lured to his death on the promise of getting it back.
Victim Dogan Ismail, 17, died from a single stab wound after a confrontation with four males on the Aylesbury estate in Walworth, South East London.
Detectives are still trying to find a 15-year-old schoolboy wanted after the killing.
Police want to interview 15-year-old Dawda Jallow who has been missing since the stabbing on Sunday afternoon.
It is believed Dogan's younger brother was the victim of an unreported mugging on December 28 - the Friday before - in which a mobile phone was stolen.
Police believe the reason Dogan was on the Aylesbury estate on Sunday was to try to recover the stolen device.
"The line around him being lured there - I'm aware of that information, but it is not something that has been given to us directly, and we will pursue that with other lines of enquiry," Detective Chief Inspector Matt Bonner said.
A schoolfriend, who wished to remain anonymous, told Sky News a text message was sent inviting them to come and retrieve the phone.
Police have appealed for help in finding Dawda and warned the public not to approach him.
"I am seeking help from the local community to locate Dawda Jallow," said DCI Bonner. "I appeal to anyone who knows of his whereabouts, or has any information that could assist us, to come forward.
"If Dawda is seen, please do not approach him but contact police."
He added: "I appeal direct to Dawda to present himself at a police station so this matter can be dealt with."
A small part of a first-floor landing in the estate's Latimer House block has been cordoned off and flowers have been laid there.
A few feet away flowers have been left for another murder victim, Shaun Chambers, 21, who died at almost the same spot in a gangland attack in September.
Police say they believe the two attacks are not linked in any way.