26-year-old Abraham Badru was gunned down in Hackney, east London, on Sunday.
He was a churchgoer and recently received a bravery award for intervening in a sex attack on a teenage girl.
Police said he was shot while opening the boot of his car to look for a drink.
The Metropolitan Police said just before the attack – at around 11.10pm – Mr Badru had parked his black Mercedes on Ferncliff Road when he was approached by a suspect or suspects.
He had not planned to be home at that time, but had returned due to a change of plans.
Paramedics and police were called to the scene, but Mr Badru was pronounced dead.
A black male, believed to be wearing a black puffer jacket, walked along Ferncliff Road in the direction of Downs Park Road and through a nearby alleyway after the sound of a gunshot, officers added.
His family have said they are devastated by his death, describing the pain as “unbearable.”
“He was shot by person/persons terrorising the peace of the community, terrorising innocent people, threatening our freedom on our streets and threatening our progression.
“We plead with any parent, siblings, extended family, friends, associates, in desperation that if you have any information to please come forward.”
Police said Mr Badru – described as a “talented young man with ambitions and so much to live for cut down in his prime” – was not intending to be home and his return was due to a change of plans.
Detective Chief Inspector Noel McHugh said: “The answer to Abraham’s death lies in the community. I know that people are talking about what happened.
“It is something truly out of the ordinary, a community hero being murdered.
“His family and friends cannot comprehend what has happened, and there are no words that can adequately describe the pain Abraham’s family are going through.
“Such courage and an overwhelming sense of what was right and wrong clearly demonstrated his strength of character.”
There have been two further violent deaths in London this month, with a 16-year-old boy becoming the youngest murder victim in London so far this year, succumbing to his wounds after he was fatally shot.
The teenager, who was shot in the face in Walthamstow, east London, at around 10pm on Monday night, died in hospital with his family by his bedside on Tuesday evening.
His death came after that of Tanesha Melbourne, 17, who was gunned down around 30 minutes earlier just three miles away in Tottenham. (Telegraph)