Rajesh Tripathi, 25, was hit by a bullet fired from the service revolver of Sub-Inspector Sita Ram who was apparenly unaware that his gun was loaded during the mock drill at Rohini West station in north Delhi, a senior police official said.
Tripathi, a resident of Madhya Pradesh, was taken to Baba Bhim Rao Ambedkar hospital where doctors termed his condition as critical.
Police registered a case of negligence and obtained the close circuit television footage from the metro station to ascertain the exact sequence of event.
CISF has also ordered a probe into the incident as according to CISF spokesperson, officials cannot carry loaded weapons during mock drills.