A pistol believed to have been used in a shoot-out between two kidnappers and police in Tsim Sha Tsui last week was discovered in an alley in Mongkok yesterday after the girlfriend of one of the two suspects was arrested. The pistol was found off Nathan Road at about 1.30am and taken away for examination. The girlfriend of mainlander Lai Kong-hung, 26, who has been charged with offences relating to the alleged kidnapping of businessman So Cha-tong, 80, is a Hong Kong resident in her 20s. She was arrested when officers from Kowloon West regional crime unit raided her Cheung Sha Wan office on Monday afternoon. She has not been charged. Lai and another unnamed man are alleged to have detained Mr So against his will 'to procure a ransom or benefit for his liberation'. Lai was remanded in custody after a hearing at Kwun Tong Court on Saturday. The case was adjourned to February 18 for an identification parade.