The security chief yesterday described the killer of a bank guard shot dead during a robbery on Wednesday as a 'cold-blooded and brutal' murderer. As the hunt for father-of-four Zafar Iqbal Khan's killer intensified, Secretary for Security Regina Ip Lau Suk-yee condemned violent crime, saying there would be no let-up in the police crackdown to prevent such incidents. Police have declined to confirm or deny media reports that the .38 calibre weapon used to kill Khan, 31, may have been a stolen police revolver. Khan - who earned $9,000 a month - was shot in the head, stomach and wrist when he tried to stop the robber, who escaped with $490,000 and US$1,000 (HK$7,800) from a Hang Seng Bank branch in the Belvedere Garden shopping arcade in Tsuen Wan. Mrs Ip's comments came as police described the killing as 'vicious and callous' and promised they would spare no effort in tracking down the culprit. 'Initial investigations show the incident involved a lone culprit. There is no evidence of syndication,' a police spokesman said. 'It is not appropriate at this stage to disclose any further information as it will jeopardise the investigation. However, police will spare no effort in bringing the culprit to justice.' He did not say whether the weapon used by the killer was a stolen police revolver. On March 14, constable Leung Shing-yan was killed and his loaded revolver and six rounds of ammunition was stolen in Tsuen Wan. Police have offered a $1 million reward but the killer is still at large and the gun has not been recovered. Tsuen Wan district commander Chief Superintendent Au Ka-hing said police officers had been asked to stay alert. 'At present, beat police officers have to go in pairs while patrolling outside all banks and goldsmith and jewellery shops in the day in the New Territories South region,' he said. Mr Au said a photofit of the killer would soon be issued to all frontline police officers after several domestic helpers who witnessed the robber taking off his balaclava were located yesterday. The bank's chief executive, Vincent Cheng Hoi-chuen, staff, and the victim's relatives attended a mourning ritual before the bank opened yesterday. Mrs Ip said the SAR was still one of the world's safest cities. The number of crimes had dropped from 64,458 in the first 10 months last year to 60,526 in the same period this year. The situation with bank robberies, which increased to 52 between January and November this year from 18 in the whole of last year, was being monitored, she said.