With the arrest of the fourth and last suspect, an aspiring doctor, the Noida Police on Thursday claimed to have unravelled the mystery of murder of a trader's 14-year-old son, who had gone missing on May 1 and found dead four days later.

Three of the accused, Manoj Sharma, Himanshu Chaudhary, and Kunal Bhati, were arrested on Wednesday, while Himanshu's girlfriend Tanvi, an MBBS student, was held Thursday, the police said.

Greater Noida resident Krishna Kumar Sharma's son Kunal Sharma had gone missing from outside their restaurant on May 1 from Beta 2 Police Station area.

A CCTV footage showed him walking behind a woman and sitting inside a car near the restaurant. On May 5 his body was found in a canal in adjoining Bulandshahr district.

The murder drew flak for the police, with the family and relatives of the dead boy questioning law and order, alleging laxity in probe.

BJP leaders Mahesh Sharma and Dhirendra Singh met with the family. Singh, the Jewar MLA, even wrote to the UP government, demanding high level probe into the case.

Additional Commissioner of Police (Headquarters) Babloo Kumar, flanked by DCP Greater Noida Saad Miya Khan, on Thursday told reporters that all four suspects in the case have been arrested.

It was a loan that the boy's father Krishna Kumar Sharma had given to Manoj and Himanshu that formed the kernel of the antagonism. The two were unable to repay the loan and conspired to kill the teenager.

According to police, Manoj, 42, is a relative of Sharma and worked at the restaurant with the family. He owned the restaurant but had to hand over its operation to Sharma in January this year as he was unable to clear the Rs 2 lakh loan.

Himanshu, 24, had also taken a similar amount of loan from Sharma but he, too, could not repay it and both were peeved over the situation.

Kunal was managing the daily affairs of the restaurant and Manoj planned the murder with Himanshu with a thought that this would break Sharma and he could have the control of the eatery back to him, the police said.

"During inquiry, the accused accepted that they committed the crime and said the main conspirator were Manoj Sharma and Himanshu Chaudhary. These two were known to the boy and his father. Manoj Sharma was operating the dhaba with the father of the boy in partnership, while Himanshu had borrowed some money from the father," Additional CP Kumar said.

"Himanshu was worried because he was being frequently asked to return the money while Manoj wanted to gain total control of the dhaba, hence they planned to kill the boy. Himanshu roped in two of his friends,Kunal Bhati and the woman, to execute the plan. They disposed the body in the canal in Bulandshahr the same night," he said.

According to police, on May 1 the woman called Kunal who was at the restaurant to come and meet Himanshu in the car, which was parked on the road outside.

Once inside the car, he was overpowered by Himanshu, Kunal (Bhati) and Tanvi and then taken to a flat in Jaypee Wishtown Sector 127, Noida. Manoj stayed with Kunal (Sharma's) family, pretending to be unaware of everything, the police said.

"At the flat, the accused thrashed Kunal and hit his head on the wall, after which he collapsed and died. His body was stuffed in a trolley bag. Later they took the bag in the car to Bulandshahr and dumped the body in the canal. The accused then kept changing their hideouts to evade arrest," Kumar said.

Meanwhile, police conducted searches at several locations.

On May 5, the body of the boy was found in the Gang Canal in adjoining Bulandshahr district and was sent for post mortem.

According to Kumar, 11 police teams were involved in the operation.

It was DCP Greater Noida's team which cracked the case on Wednesday by arresting three suspects, including one who got injured in a gunfight with the police, he said.

The senior IPS officer said the Skoda Rapid car used by the accused in the crime has been recovered and the clothes of the victim have been recovered from the car.

"During inquiry, the trio confessed to the crime and on their inputs, the fourth accused, a woman, has also been arrested. Evidence connected with the case like mobile phones of the accused have been recovered from a drain where they were dumped. "Along with this, various car stickers and tapes which they had purchased from a market in Noida have been recovered," he said.

The clothes which were worn by the accused during the crime and later hidden, have also been recovered. The accused had used a trolley bag to transport the body of the boy and that bag has also recovered, he added.

"The sensational but unfortunate case has been successfully worked out by our team. The police commissioner has announced a reward for the police team involved in the case," Kumar said.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.