A tip-off may have led to the apprehension of the man who plotted an attack involving two of the city's most prominent citizens, according to senior law enforcement sources. Jurors at the trial of the Shenzhen man, Huang Nanhua, 50, were told that he had been stopped in a taxi by officers during a routine roadblock in Dundas Street, Mong Kok. 'He was intercepted quite by chance,' prosecutor Peter Chapman told jurors at the trial in the Court of First Instance. And an official police spokesman reiterated yesterday that Huang's arrest had followed an 'anti-crime snap check' at 10.18pm on August 14, 2008. 'Upon searching the passenger, a handgun and five bullets were found inside a bag carried by him. Police arrested the man for possession of a firearm and ammunition without a licence,' the spokesman said. But one senior police source said he had heard that Huang's arrest had been a planned takedown. Another source familiar with the case said that he understood police had received a tip-off as to Huang's intentions. The fact that Huang's initial arrest was handled by the West Kowloon regional command and then quickly handed over to the organised crime and triad bureau also suggested that an informant had told police about the scheme and those involved, another police source said. That leak might have come from a person who wanted to reduce their sentence on upcoming criminal charges, the sources said. The trial was not told who hired Huang and several other men who remain at large. Huang had a gun, bullets and details about former Democratic Party chairman Martin Lee Chu-ming and publishing tycoon Jimmy Lai Chee-ying when he was arrested. He was sentenced to 16 years in prison on Friday after being found guilty of possession of a firearm with intent to commit an arrestable offence. The trial heard that dozens of armed police officers swarmed Huang when he refused to hand over a shoulder bag for inspection at the roadblock. That bag contained the gun and ammunition. Huang was pinned to the ground before officers hauled him away in a police van, the court heard. Meanwhile, sources said that the foiled plot was well known among senior officials before it was exposed by the South China Morning Post just weeks before the trial. 'It was strange that it did not come out earlier,' one officer said.