The incident occurred at Manzoor Shaheed police station on Eastern Bypass when the constable engaged in an argument with the officer, said SP Sariab area, Abdullah Jan Afridi.
Subsequently, the policeman opened fire at the officer, killing him and one personnel, while injuring another, he added.
Four policemen gunned down in Quetta
Earlier on June 28, at least two policemen were killed in Quetta when assailants riding a motorbike opened indiscriminate fire on their vehicle coming towards the city.
Hours later on the same day, armed men opened firing on a police mobile, killing the mobile driver and another personnel on the spot.
Quetta is among the most volatile cities of Balochistan, with police personnel regularly targeted, apparently to fail efforts aimed at restoring law and order in the province.
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