A 30-year-old man was allegedly shot dead by four persons, including a retired Delhi Police sub-inspector and his youngest son, just outside his house at Sarvodaya Nagar in Vijay Nagar area here on Friday night.
The victim, identified as Ankur Pandit, was accused of killing two sons of the retired policeman, Jwala Prasad.
Pandit's family has named Jwala Prasad and his son Robin in the FIR.
The duo has been detained. The other two culprits are at large, police said.
"We have detained them. They might have hired killers to eliminate Pandit. We are yet to ascertain their involvement and are working on other angles too," said Raghuvir Lal, SSP.
The incident took place when Pandit alighted from his car outside his house around 11pm. He was allegedly attacked with 7.65-mm-bore pistols.
He sustained three bullet wounds, police said. The police have recovered three empty cartridges from the spot.
Police said Pandit had murdered Jwala Prasad's eldest son Jyoti, 35, in January 2009. He was arrested in this case and had got out on bail six months ago.
He was also named in the murder of his younger son, Rajeev, 30, who was pursuing Jyoti's murder case at Ghaziabad court, police said. Rajeev was murdered in January 2010 in Vijay Nagar.
"The first murder took place as Pandit and Jyoti had an altercation over a woman. This incident created feud between the two families," said Lal.
According to the police, Pandit was also said to be involved in the sale and purchase of many properties in Vijay Nagar area.
Police said in 2010, Pandit's father, Kripa Ram Pandit, was found dead under mysterious circumstances.
His family had named Jwala Prasad and his family members in the murder case, which was registered on court's directions under Section 156(3) of the CrPc.
Later, the police submitted a final report.