According to the police, the accused have been identified as Mohit Bhati, 29, and Pooja, 26, residents of Gautam Budh Nagar in Uttar Pradesh and Ghazipur in east Delhi.
On a tip-off, Mohit was arrested first on Sunday from near his residence, after which Pooja was also arrested the same day.
The police said the incident occurred on Saturday morning when deceased Manoj Kumar, brother-in-law of Pooja, went for buying a water bottle from a nearby shop in Ghazipur. Mohit, who was waiting for Manoj on a bike, shot him dead with a country-made pistol.
"When Manoj Kumar did not return to his residence, Pooja went looking for him and found him lying in a pool of blood. She later informed the police," Deputy Commissioner of Police Pankaj Kumar Singh said.
"During interrogation, Mohit disclosed that he was a friend of his neighbour Mukesh Kumar, husband of Pooja, in Gautam Budh Nagar. He started visiting his house and befriended Pooja. He and Pooja later developed physical relationship. But when their relationship came in the knowledge of Mr Mukesh, he started fighting with Pooja," the officer said.
"Manoj, after the death of his brother Mukesh, took Pooja to Delhi and started living in Ghazipur village. But in his absence, Mohit once again started meeting Pooja. Manoj later knew about the relationship of Pooja with Mohit and he would object to it," the officer said.
"Bhati and Pooja decided to kill Manoj and as per their plan, Mohit shot dead Manoj on Saturday," he added.
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