The incident occurred at around 10:40 AM at Rohini West metro station when a mock-drill was being conducted by CISF, Delhi Police and Delhi Metro Rail Corporation (DMRC).
During the drill, sub-inspector Sitaram fired an accidental shot from his 9mm pistol which hit constable Riptesh Tripathy in the lower abdomen.
He was immediately taken to a hospital and is said to be out of danger.
"The sub-inspector has been suspended and a court of Inquiry has been ordered by the force," a senior official said, ruling out any foul play in the incident.