The son of an assistant commissioner of Delhi Police was allegedly pushed into a canal in Haryana by two of his friends over a financial dispute, police said on Friday.
A search operation has been launched to trace 26-year-old Lakshya Chauhan, they said.
One of the accused has been arrested while efforts are underway to nab another, they added.
Chauhan, along with two of his friends - Vikas Bhardwaj and Abhishek - had gone to attend a marriage function in Haryana's Sonepat on Monday, the police had said on Thursday.
After he did not return home the next day, his father ACP Yashpal Singh, posted as ACP (Operations) in Outer-north Delhi, lodged a missing complaint on Tuesday, they said.
The complaint was later converted into an abduction FIR when the police suspected some foul play during investigation, they added.
The section of murder was added to the case on Friday and one person was arrested in connection with the case, an official said.
Chauhan, who resided with his parents in outer-north Delhi's Samaypur Badli area, was an advocate and practised at the Tis Hazari court, the official said.
His friend Bhardwaj works as a clerk for another lawyer who practises at the Tis Hazari court, while Abhishek (19) is his acquaintance, who was detained on Thursday for questioning, he said.
During interrogation, Abhishek said Bhardwaj called him on Monday noon and invited him to attend a marriage function with him and Chauhan in Sonepat, the official said.
Bhardwaj had also told him that Chauhan had taken a loan from him and misbehaved whenever he asked him to return the money. The duo then planned to eliminate him, he added.
On Monday, Chauhan picked the accused from near Mukarba Chowk in Rohini here. They reached the marriage function by night and left after 12am, another official said.
While returning, the trio stopped the car on the roadside near the Munak Canal to attend nature's call. This is when Bhardwaj and Abhishek allegedly pushed Chauhan into the canal and fled the spot in his car, the official said.
When the accused reached Delhi, Bhardwaj dropped Abhishek in Narela and went away, he said.
Abhishek was picked up from his house in Narela on Thursday, the official said.
Based on Abhishek's statement, he was arrested and Sections 302 (murder) and 201 (causing disappearance of evidence) of the Indian Penal Code were added to the FIR, he added.
The police said efforts are being made to trace Chauhan and his car and arrest Vikas.
