Twenty-two-year-old Sheikh Salman confessed to killing his friend, 20-year-old diploma engineering student Syed Salauddin in Birbhum’s Choupahari forest the early hours of Sunday after the battery of the victim’s mobile phone, which Salman had been using to demand Rs 30 lakh as ransom, died.

Police sources said during interrogation Salman confessed that as soon as Salauddin’s phone battery died, he realised there was no chance to get the ransom money as the line of communication with Salauddin's family had snapped.

Salauddin’s father owns a stone-crushing unit in Birbhum’s Mallarpur. Salman was also afraid that if Salauddin, who the former had forced to drink a good quantity of liquor, regained consciousness, his crime would be exposed.

“The accused was not a professional killer. He used the mobile phone of the student to hide his identity. But by 2am on Sunday the mobile phone ran out of power for which he was not prepared. He lost the chance to get the ransom amount due to lack of communication. Salauddin was slowing regaining consciousness and he saw that as a threat,” said a senior police officer in Birbhum.

Salauddin, who studied at a private college near Asansol, went to Khoirasol in Birbhum to visit his extended family on Saturday like he often did. Salauddin and his family knew Salman for years. Salman, a college dropout, owned a brick kiln in Khoirasol and was “deep in debt”.Salauddin’s body, with his throat slit and other stab wounds, was recovered from Choupahari forest on Sunday morning.

Police arrested Salman within a few hours of recovering the body by tracking Salauddin’s phone location.

“Our team started working late Saturday night once the family members reported about the (ransom) phone calls and abduction. So it was possible to arrest him so early,” said Birbhum police chief Nagendra Nath Tripathi.On Monday, Salman was produced before a Bolpur court that sent him to seven days in police custody.

“I have a huge debt in the market and I did it because of money. I am ashamed of what I have done,” Salman told reporters when he was taken to the crime spot by cops to confirm multiple locations where he stayed with Salauddin since Saturday night.Salauddin’s family members said they doubted if the murder was a handiwork of one person.

“We think it was a planned murder and more than one person was involved. We have requested police to probe into it," said Syed Adbul Mayeen, the victim’s uncle.Police have said that investigation so far pointed at Salman as the lone murderer.“The probe is not over. But all evidences suggest Salman was at the crime scene alone,” said a senior police officer. On Monday, a team of forensic experts from CID collected samples from the crime scene.