A Central Industrial Security Force constable on guard duty outside the Rashtrapati Bhavan was found dead with gunshot wounds on Wednesday, police sources said.
Constable Krishna Kumar had bullet wounds on his upper torso and head, they said.
Police said they were investigating whether it was a case of suicide or accidental firing as no suicide note had been found at the sentry post outside the presidential residence where Kumar was on duty.
The incident took place overnight and was reported to police by Kumar's colleagues.
A fortnight back, a CRPF jawan posted at Union Minister Dayanidhi Maran's residence had shot dead his senior colleague, apparently due to some personal enmity.