Azamgarh police arrested on Monday a 28-year-old man, Nazirudeen, for a triple-murder and double -rape in the Uttar Pradesh town on the intervening night of November 24 and 25. Azamgarh senior superintendent of police (SSP) Triveni Singh described Nazirudeen as a "psychopathic sexual offender," and a "deviant".

The incident came to light on the morning of November 25 when the bodies of a couple and their 4-month-old son were found in a house in the Mubarakpur police limits. Two other injured children, a nine-year-old girl and a five-year-old son, were also found in the house. The incident created panic in the area.

Singh said the police zeroed in on the accused after analysing mobile tower data and his phone's location at the time of the incident. A background check revealed that he was a "sex maniac", the SSP said.

"His wife had left him recently because of his deviant behaviour. He also visited prostitutes, some of whom had banned him because of his behaviour," he said.

"This [phone] data as well as [the] history of his behaviour towards women helped us in cracking the case," he added.

Singh said the accused confessed during interrogation that he conducted a dry run.

"Once he determined that the woman's house was located in a place from where screams would not be heard by other villagers, he decided to commit the crime," he said. "He scaled the boundary wall of the house after midnight and attacked the woman's husband with a stone, expecting him to pose the maximum resistance.

"He hit the woman and her daughter when they tried to raise an alarm. After that he attacked the other two children," said the SSP.

He said the man and the baby died immediately, while the woman died after some hours.

Nazirudeen raped the 30-year-old woman and her nine-year-old daughter. The other two children are undergoing treatment at a hospital in Azamgarh and are in a stable condition, said the police. Singh said, "The accused raped the woman and her daughter at least twice during his three-hour stay at their house. "

The SSP said: "Nazirudeen told us during interrogation that he made videos of the crime on his mobile phone. "

The accused has been booked under various sections of the Indian Penal Code and Protection of Children from Sexual Offences (Pocso) Act 2012.