The Bagchis are the residents of Hari Ghosh Street in Burtolla. DC (HQ) Vineet Goyal said that Diwakar has told the police that he saw his father smothering his mother with a pillow.

“I woke up as I heard sounds of struggle. My father was drunk. As soon as I started shouting, he tried to strangle me with a cotton towel. I bit his hand and ran out of the room.” said Diwakar.

On Monday night, family members, including Swarnali’s mother Kalyani Sanyal, woke up to Diwakar’s screams and rushed to the room only to find Swarnali unconscious.

After rescuing Diwakar and bolting Bagchi in the room, they informed the police.

Both mother and son were rushed to the Calcutta Medical College and Hospital, where Swarnali was declared “dead on arrival”.

According to the police, boy’s eyewitness account of the crime is most crucial to prove the case against Bagchi.

During interrogation, Bagchi said that he was under depression due to the huge debts that he had incurred.