A 50-year-old man, who worked as a security officer, allegedly shot dead his wife and son after a domestic dispute at their residence in Gurugram's Ashok Vihar colony in the early hours of Sunday, police said.
The accused, identified as Anil, possessed a licensed pistol. He was later taken into custody, and an FIR has been registered at the Palam Vihar police station, they said.
His wife Asha (45), principal of a private school, and son Prashant (25) died in the incident.
According to the police, the couple frequently quarrelled and had an argument late on Saturday night.
During the altercation, Prashant, who was sleeping in another room, woke up after hearing loud voices and attempted to intervene.
Anil allegedly pulled out his licensed pistol and opened fire on his wife and son, killing both on the spot, the police said.
Residents said they heard multiple gunshots from the house and rushed to the spot. On finding the two lying in a pool of blood, they alerted the police.
Police and forensic teams reached the scene, inspected the house and collected evidence.
The premises were later sealed for investigation.
Officials said that when police arrived, Anil was found sitting near the bodies.
The victims were taken to a civil hospital where doctors declared them dead.
Police said Anil had earlier worked as a physical education teacher and sports trainer in schools before joining a private company as a security officer.
"We are questioning the accused and reviewing his records. The bodies will be handed over to the family after the post-mortem. Further investigation is underway," a senior police officer said.