CHENNAI: A probe into the murder of a 57-year-old bank official in Velachery last Thursday led investigators to a concoction of unnatural sex , blackmail and retribution.

Police arrested four youngsters on Sunday for the murder of N Nagarajan, assistant manager of Tamil Nadu State Cooperative Bank , Besant Nagar. All four arrested suspects are juveniles and students. Investigators are searching for a fifth suspect, Gowtham, 20, who works at a showroom in Nungambakkam.

They told police officers that Nagarajan first paid them to have sex with him. When they tried to break free of his clutches, the bank official blackmailed them repeatedly, threatening to inform their parents about what they had done, if they did not comply.

Nagarajan met the youngsters in 2008, when he was assistant manager with TNSC Bank in Kasimedu, an investigating officer said. The lure of quick money proved too strong for the boys to resist and Nagarajan started a string of seedy relationships with them.

“He would invite the boys home, offer them food and lure them into bed,” Velachery inspector V Muthuraja said. “The boys were too young to understand the consequences of their actions.”

The boys Nagarajan first had relationships with introduced their friends to the banker. “Over time, the boys wanted to end their association with Nagarajan. But he warned them that he would tell their families about what they had been up to,” the inspector said.

The five youngsters decided that they would not be exploited any more and, when Nagarajan called them home on the night of October 16, they decided to eliminate him. When they entered Nagarajan’s bedroom in the upper floor of his duplex apartment in Baby Nagar, Velachery, one of the boys hit him on the head. When he fell, two others strangled him with their hands. They punched him repeatedly before two of the boys removed his belt and used it to strangle him. “He could have already been dead by the time they strangled him,” inspector Muthuraja said.

One suspects told the police that they wanted to hurt Nagarajan. “They decided to throw chilly powder in his eyes. One of them ran downstairs to get chilly powder as the others assaulted Nagarajan,” Muthuraja said. “Nagarajan’s 87-year-old mother Kamala was downstairs but she did not suspect anything was amiss because the boys were regular visitors.”

After killing Nagarajan, three of the youngsters took his cellphone and gold ring and walked to Perungudi Railway station. The two others took his scooter to the station and from there they boarded a suburban train to Royapuram early on Wednesday. Investigators said the fifth suspect, Gowtham, was in possession of Nagarajan’s gold ring.

Nagarajan’s wife Selvi was away in the US when the murder took place.