"The incident took place at around 12.40 pm. In the CCTV footage, the victim can be seen shooting himself with his service carbine," said Deputy Commissioner of Police (New Delhi) Madhur Verma.
He was rushed to a nearby hospital where he was declared brought dead, news agency PTI has reported. No suicide note has been found from the spot, the officer said.
Reports say Narain had resumed duty after a long vacation. At around 12:4o pm, he went near tree and pumped two bullets into himself.
Further investigation is underway.