Three unidentified motorcycle-borne assailants gunned down a 30-year-old man outside his residence in south Delhi's Sangam Vihar around 11.30pm on Friday.
The deceased was identified as Gyan Singh, an auto-rickshaw driver.
A police officer said Singh was standing outside his house when three unidentified men shot at him and fled.
Hearing the sound of the gunshot, Singh's family members rushed out and saw him lying in a pool of blood.
"Singh was immediately taken to a nearby hospital where doctors declared him dead. We have registered a case of murder and are investigating the case from all angles," the police officer told Hindustan Times.
Singh's family members alleged that he was killed by some local gamblers as he had launched an anti-gambling campaign in the locality.
As a mark of protest, Singh's family members and neighbours came out on the road near Batra Hospital and blocked traffic around 11am on Saturday.
They shouted slogans against the Delhi police and demanded justice for the deceased.
Meanwhile, the family members also alleged that Singh had lost his life due to the lackadaisical approach of the police in stopping gambling in the Sangam Vihar area.
The flow of traffic was affected due to the protest, causing inconvenience to commuters.