Assistant Commissioner of Delhi Police Rajbir Singh was shot dead late Monday by a property dealer in Gurgaon, a police official said.
"We have arrested one Vijay Bhardwaj for murdering Rajbir Singh. Rajbir was alone at Bhardwaj's office on Mehrauli-Gurgaon road when he was shot dead," Gurgaon police commissioner Mohinder Lal said on Tuesday.
"The weapon used in the crime has been recovered but we are not sure about the number of gunshots fired by Bhardwaj," Lal added.
The police commissioner refused to give further details.
Vijay Bhardwaj confessed to killing Rajbir Singh. "He (Rajbir) was pressurising me to give money and had threatened to kill me. I failed to arrange the money so I killed him," Bhardhwaj told reporters, before he was whisked away by the police officials.
Singh's body has been sent for post-mortem examination and the forensic teams were collecting evidence from the crime scene.
Rajbir Singh headed the special operations squad of the Delhi Police's crime branch and was also involved in the successful investigation of terrorist attack on parliament in 2001.
Singh, who had served for six years with the Delhi Police special cell, had earlier been transferred to Delhi Armed Police (DAP) and later to the traffic department after tapes of his purported conversations with a contractor on a land deal were made public.
Later, a vigilance probe gave him a clean chit stating that a retired police official connived with others and recorded his phone calls illegally to settle scores with him.
Rajbir Singh started off his career as a sub-inspector in 1982 and climbed up the hierarchy through a series of encounters. Singh was involved in nearly 50 encounters.