Detectives hunting the killer of a “community hero” who was shot dead near his home have urged witnesses to “do the right thing and bring justice” to his grieving family.

Abraham Badru, 26, was gunned down in Hackney, east London, on March 25 after opening the boot of his AMG Mercedes to look for a drink. He was on the phone to a friend when he was shot in the chest.

Police say his killer, who may have been lying in wait, escaped on a white bike with no lights, and have given details of four people who were near the scene that they want to trace.

Detective Chief Inspector Noel McHugh said: “Abraham was an ambitious and talented young man who had everything to live for. He did not deserve what happened to him and his family do not deserve the torment they are suffering now. We are now a month on and every day his family have to live knowing that the person who did this is still out there. Someone knows who killed Abraham; I have said the answer lies in the community and I still believe that.

“If you are reading this and you want to contact us but are concerned about your safety, I can assure you that your information would be treated in the strictest of confidence and sensitivity. Help us do the right thing and bring justice to Abraham’s grieving family.”

One line of inquiry is whether his murder was linked to an act of bravery in 2009 when he saved a teenage girl from being raped, and gave evidence against her attacker in court. Police are also looking at his love life and his business interests.

The four people are:

– a person who walked along the pavement in Langford Close and then turned into Ferncliff Road at 11.08pm, minutes before the murder

– a person wearing a three-quarter length puffa jacket who was opposite the day centre in Ferncliff Road, close to the scene, at 11.09pm

– a man who was wearing light-coloured trainers and dark clothes with his hood up, talking on a mobile phone in Ferncliff Road at 11.11pm, minutes after the shooting as Abraham lay on the ground

– a black man, around 5ft 8in with bushy Afro hair and an athletic build, who was wearing a long-sleeved grey top and ran into Foxley Close from Ferncliff Road shortly after the shooting

Mr McHugh added: “We are keen to trace each and every person who was in the area that night – even if you think you didn’t see or hear anything we need to eliminate you from our enquiries. It may be you have information you don’t think is relevant but please let us be the judge and come forward. I have outlined four people we’d like to trace but we really need to speak to everyone.

“We are particularly keen to hear from anyone who saw a male cycling in the area around the time of the murder on a white bicycle – this could be the killer.”

Police will return to the scene of the murder on Wednesday, a month since the killing. A £20,000 reward is on offer for information leading to the arrest and prosecution of the murderer.

Anyone with information can contact police on 020 8785 8099, via 101 or @MetCC. Or to remain anonymous call Crimestoppers on 0800 555 111.