AIG, STF, Snehdeep Sharma said the Head Constable used to hand over heroin to his accomplices.
One of the accused is already facing a trial in a drug peddling case lodged at Tibba police station. Police had announced a bounty of Rs 2.5 lakh on his head.
An STF team member and accused sustained injuries during the encounter, following which all were shifted to a nearby hospital for medical aid.
Two pistols, live cartridges, and a car have been seized from the accused possession.