The police, investigating the double murder of a couple in Memari, North 24 Parganas, are also looking into the “disturbing transformation” of the accused — the couple’s 35-year-old son Humayun Kabir, who once worked as an engineer in Delhi.

Police said on Friday that the investigation so far reveals that Kabir, who once held a reputable job in Delhi developed a keen interest in “jihadi literature” and had several such videos on his laptop and mobile.

The police are now investigating if he had “extremist links”.

Kabir allegedly murdered his parents on Wednesday and fled to another district, police said. His desperate flight ended later the same day in Bangaon, where police apprehended him after he allegedly stabbed and injured four more persons.

Mustafizur Rahman (65) and his wife Momtaz Parveen (56), residents of the Kashiara Kazipara area in Memari town, were found murdered outside their residence on Wednesday morning. They informed the police, who sent the bodies for autopsy.

According to the police, Kabir’s life “took a dark turn after his divorce a few years ago and he suffered from depression.” “Kabir would spend nights glued to his laptop, watching videos of atrocities,” said an officer.

“He was a good student and secured a coveted job through campus recruitment in Delhi. Yet, even during his work breaks in Delhi, he was absorbed in his video collection,” said the officer.

While on the run, Kabir switched off his phone and deactivated all his social media accounts, attempting to erase his digital footprint, police said.