The body of Sharath N, the 19-year-old son of Niranjan Kumar, an income tax officer from Bengaluru, was discovered near a lake in Kengeri, on the outskirts on Bengaluru on Friday morning.
They believe the abductors killed the teenager because they feared being caught.
On the evening of September 12, Sharat had left home in his new motorbike, saying that he was going out to meet his friends.
However, when he did not return home till 8.30 pm, his parents got anxious.
The boy was studying automobile engineering at Acharya Institute of Engineering.
The Gnanabharati police arrested six persons in connection with the crime on Thursday night, including Vicky, Vinay and Vishal.
On 15 September, a report in Bangalore Mirror noted that Sharath was kidnapped and the kidnappers had demanded Rs 50 lakh ransom. Later, the victim's mother received a Whatsapp video from the victim's phone. They had first dumped the body in Rachenahalli lake, India Today reported. Post this, a complaint was registered with the police.
In the video, taken in a vehicle, Sharath is seen informing his father that he has been kidnapped by someone 'who suffered at your hands, ' and asking for a ransom of Rs 50 lakh to free him. Sharath reportedly told his parents that the kidnappers looked like terrorists and could also harm his sister. The police were sceptical because except the video, the kidnappers had tried to contact with the family.