Constable S Ramesh Reddy was cleaning the rifle at the District Treasury office in the Collectorate building here when the incident took place around 6 AM and the bullet pierced his stomach, Sangareddy police said.
Reddy was on his routine duty and died on the spot.
The body was shifted to the government hospital here and after the postmortem it was handed over to relatives.
Reddy was a native of Pulivendula in Cuddapah district and had joined police force in 1991.