The arrested persons were identified as Hindi teacher of the school Naziya Hussain, her husband Arif Ali Ansari and their 12-year-old daughter and 16-year-old son, Senior Superintendent of Police Kuldeep Dwivedi told reporters here.
Alleged love affair appeared to be the motive behind the killing, the SSP said.
The couple's 16-year-old son, who was upset over the alleged affair, had invited the boy to their residential quarters in the school for having food around midnight on February 4 and the CCTV footage showed the victim Vinay Mahato passing through the residence of the school Principal to reach the teacher's house, the SSP said.
He 'warned' Mahato to stay away from his sister, the officer said quoting preliminary findings.
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When the boy reportedly spurned his warning, the son allegedly gagged Mahato's mouth before he started punching him in the stomach and smashed his head against a wall, the SSP said.
The son thought the profusely bleeding Mahato, who fell unconscious, was dead.
Meanwhile, Nazyia, who was sleeping, was shocked to see a bleeding Mahato and they allegedly dragged him out of home and hurtled down the corridor as they did not find any place to hide the body and allegedly cleaned blood-stained spots, the police officer said.
Mahato was immediately rushed to the Rajendra Institute of Medical sciences but he succumbed to his injuries on way, the SSP said.
The police officer said the investigation of the case involved sniffer dogs and sleuths of the forensic department and the CID.