A man shot dead on Christmas Eve was attacked in front of his family after a night out, police said.
Officers were called to Battersea Church Road in south west London at about 21:00 GMT.
Neighbours described hearing multiple gunshots followed by a woman screaming “desperately” for help.
A spokesperson for the Met Police said the killing which “saw a man losing his life in such a horrific way” had left his family “devastated”.
The 36-year-old who had a wife and young child was pronounced dead at the scene by the emergency services.
Neighbour Vittoria Amati, 60, said she heard between “eight to 10” gunshots fired.
“I then heard the screams of the wife. I came out and realised it was one of my neighbours.
“He was lying in front of his doorway in a pool of blood. He was still alive. We were really hoping he would make it.
“You have no idea how desperate she [his wife] sounded.”
A young woman, who identified herself as a nurse, tried to help the man by applying pressure to his wounds, Mrs Amati added.
Det Ch Insp Jamie Stevenson said: “Our investigation is in the very early stages and we are still working to establish what the motive could be that has led to a man losing his life in such a horrific way, on Christmas Eve, in front of his family.
“They have been devastated by this horrible event and are being supported by specialist officers.
“We know that the victim was returning home with his wife and young child following an evening out, when he was shot just yards from his home.”
The officer added the assailant fled on foot in the direction of Battersea Bridge Road.
Supt Richard Smith said: “There is no suggestion that there is any ongoing risk to members of the local community in Battersea.”
The death is the 135th homicide in London in 2019, the highest number in a calendar year since 2008.