The victim, Manmohan (40), called up the police around 11.30 pm last night seeking help after sustaining a gunshot wound to his temple, they added.
A police team reached the Mahavir Enclave area of Dabri here and found Manmohan at the residence of Surjeet Ghosh. He was rushed to the Agrasen hospital, where doctors declared him "brought dead", a senior police officer said.
"Two pistols were recovered from the spot. A case of murder has been registered and Ghosh, his wife and two sons have been detained for questioning," said the officer.
A police team rushed him to a nearby hospital where he was declared dead.
A pistol and mobile phone were recovered from the spot and a case was registered, the police said.