The police have launched a search for the second suspect in the killing of Assistant Sub-Inspector (ASI) Harjit Singh after his accomplice, Deepak Singh, was shot dead in an exchange of fire with the police in the Islamabad area here on Saturday night.The second suspect, who also belongs to Mulechak village, fled from the spot. Police teams were chasing him and conducting raids to nab him.Deepak, who was also a resident of Mulechak village, allegedly had links with Pakistan-based anti-national entities. He was facing a drug-peddling case in which around 500 grams of heroin had been recovered from his possession and was currently out on bail.ASI Harjit Singh was shot dead while on duty near the Bhagtanwala grain market under the Gate Hakima police station on the intervening night of September 17 and 18. He suffered a bullet injury to the back of his neck and died on the spot.CCTV footage, technical inputs, tower-dump data and information gathered from local sources helped investigators establish the identity and movement of the suspects.The police said a team signalled the two suspects travelling on a scooter to stop at a naka around 9.45 pm on Saturday. Instead of stopping, they allegedly opened fire at the police party and fled towards another checkpoint.At the subsequent naka, the suspects again opened fire. Two bullets hit the police vehicle, while a policeman narrowly escaped after a bullet struck his bullet-proof jacket.The police retaliated, leading to an exchange of fire. Deepak sustained gunshot injuries and was rushed to a hospital, where he later succumbed to his injuries.The police claimed to have recovered a .30-bore pistol, two magazines containing eight live cartridges, a mobile phone and an Activa scooter allegedly used in the crime.“Forensic analysis of Deepak’s mobile is being carried out, following which we will be able to identify his Pakistan-based handlers,” said an official privy to the investigations.