A 39-year-old man has been arrested from outer Delhi's Paschim Vihar area for allegedly killing his wife and two minor children, the police said on Wednesday.
The accused, Gagan Kumar Sahu, from a village in Munger district of Bihar, worked as a mason, they said.
The police said the couple used to fight often as the man suspected his wife of having an affair.
The bodies of the 28-year-old woman, her nine-year-old son and five-year-old daughter were found with multiple injuries to the heads and the faces at their rented house in Shiv Ram Park of Nihal Vihar on July 19, the police said.
A case of murder was registered and an investigation was taken up.
Senior police official A Koan said CCTV cameras were scanned and technical surveillance was done to trace the accused.
"On Tuesday, our team received information about Gagan. He concealed his identity to mislead police but was held from Paschim Vihar after he confessed his involvement in the murder," he said.
During interrogation, he told police after three-four years of their marriage, they started having altercations over domestic issues. He also suspected his wife of having an affair and on the day of incident too, they had an altercation over the same after which he smashed her head and face with a blunt object, Mr Koan said.
When the children woke up and started crying, he hit them with the same weapon and fled, he said.
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