Police are offering a reward of up to £20,000 for information about the murder of a man shot dead “without warning”.
Abraham Badru, 26, was killed in Dalston, east London, on 25 March.
Mr Badru was awarded the National Police Bravery Award in 2009 for stopping a rapist from attacking a teenage girl.
Metropolitan Police Ch Supt Noel McHugh said: “The answer to Abraham’s death lies in the community.”
No-one has yet been arrested in connection with the murder.
Ch Supt McHugh said: “I know that people are talking about what happened.
“It is something truly out of the ordinary, a community hero being murdered.”
Mr Badru, who had two sports science degrees, was described by his family as kind, bold and a “beautiful soul” who “hated confrontation”.
He was attacked after he parked his black Mercedes in Ferncliff Road, near an alleyway leading to Langford Close and Foxley Close.
He was approached by one or more suspects as he opened his car boot before being shot in the chest.
Emergency services were called at about 23:00 GMT but Mr Badru died at the scene.