The police had earlier arrested a couple from near the borders of Bangladesh for allegedly killing a retired education officer Dinabandhu Mallick, his wife Nirmala and their two minor daughters aged ten and four years.
The police arrested Dinabandhu's co-brother Fakir Mallick from Nayagarh district on charges of murder, criminal conspiracy and intimidation and forwarded him to court on the day, the crime branch sources said.
Fakir was a suspect and under scanner ever since the murder took place as he was the one who introduced the arrested couple- Rahim Khan and his wife Ayesha Begum, from Chhatisgarh to Dinabandhu.
Arrested on October 9, the couple was on police remand for last four days. On the basis of the interrogation, the police have recovered the weapons of offence - two swords from the house of Mallick.
Acquainted with the family, the couple had arrived at Mallick's place late in the evening of September 21 and after dinner had stayed back in their house.
However, late after midnight, the couple killed the Mallicks by slitting their throats with the knives they had brought with them and decamped with some valuables from the house.