A mother has appealed for information about her 27-year-old son's killer "before he hurts anyone else".
Daniel Herbert, was found on 17 August in Clements Road, Bermondsey, south-east London, with a gunshot wound to the head, fired at close range.
His mother Androulla Herbert, 46, said: "They beat him and shot him afterwards as if it wasn't enough."
Mr Herbert was chased by a gang who beat him before forcing him to kneel and shooting him, police said.
Holding a picture of her son, Mrs Herbert, a supermarket worker from Orpington, south-east London, said: "Daniel was my only child, I have got no other children.
"Someone out there, help me find Daniel's murderer please, before he hurts anyone else."
Describing her son, she added: "He was a joker, loud, funny, a big presence.
"I go on Facebook and I see everybody has got only good words for Daniel and I ask why would someone do that to him?
"I just feel numb. I am waiting for him to come home so I can have a go at him for putting all of the family through this."
Robbery is not said to be the motive for the killing of the nightclub promoter, who was chased through the streets near Bermondsey Tube station before he was shot.
Det Ch Insp Cliff Lyons said: "Daniel was chased by a gang of men, predominantly white males, four to five white males, who managed to capture him in St James's Road, where they beat him unconscious.
"Having done that, they dragged him to his knees, placed a gun to his head and murdered him.
"That is a callous and brutal murder."
A 27-year-old man was arrested on suspicion of murder and released on bail last week.
Several addresses in the Bermondsey area were also raided on Tuesday night.