Scotland Yard is offering a £20,000 reward for information which helps officers find two gunmen who killed a 16-year-old boy a year ago.
Samuel Adelagun was walking with three friends on Chesterton Road, Plaistow, east London, in the early hours of October 23, 2010, when he was shot in the chest.
He died at the scene while one of his friends, a 15-year-old boy, was shot in the stomach. He recovered in hospital.
Scotland Yard said it is believed two gunmen dressed in black and wearing balaclavas fired about four shots from behind the group.
Four men aged between 20 and 23 were arrested in November last year but no charges have been brought.
Detective Sergeant Gary Royal said police remained committed to finding Samuel's killers.
"It is hoped the offer of a reward will encourage members of the public to come forward and provide information that will lead to the identification, arrest and prosecution of the person or people responsible," DS Royal said.
Samuel's mother, Ola Shokumbi, said her son's death had greatly affected her and his family.
"He is missed very much every day and his death has left a significant hole in our lives. We hope that eventually those responsible will be brought to justice," she said.
Anyone with information about Samuel's killers is asked to call police at West Hendon on 020 8733 4211 or Crimestoppers anonymously on 0800 555 111.