At least three police personnel including a DSP were killed and two others injured in an incident of firing by unidentified miscreants in Quetta, report said on Saturday. According to police sources, DSP Habibullah was on way to his office from his residence at Jail Road, when two miscreants riding a motorcycle opened indiscriminate fire on him, killing him (DSP Habibullah), ASI Muhammed Aslam and Constable Shafique on the spot.