A 19-year-old plumber who police suspect attacked a woman using a stun gun was caught after keys found at the scene led them to his house. Detectives found women's uniforms, underwear, stockings and pornographic discs hidden in the man's Shamshuipo home. The 26-year-old woman he allegedly attacked with the stun gun in her own building on Friday was wearing a uniform and stockings. Police believe the woman would have been further assaulted if her screams had not alerted a security guard. Acting Superintendent Sin Chi-sing, the assistant operation officer for the Shamshuipo district, said it was the first time a stun gun was believed to have been used in a sexual attack. Mr Sin said that according to the victim her attacker banged her head against the wall when she put up a struggle. The attack happened at about 11pm on Friday as the woman was returning from work to her Castle Peak Road home. Her attacker spotted her outside her building and followed her inside. According to police, the building security guard grew suspicious when the attacker entered, and he followed the pair's movements via CCTV. The attacker followed the woman into the elevator and when she exited on a low floor, dragged her to a staircase, police said. The guard heard the woman's cries for help and quickly sealed off the main exit of the building before rushing to the scene. But the attacker managed to flee the building via the rear exit. A set of keys, glasses and the stun gun were left at the scene. After initial investigations, detectives concluded the attacker lived in the area. They made copies of the keys and began trying the doors of nearby buildings. Five hours later, they found the right gate on Yen Chow Street. Police talked with the man's family and learned he had gone to the mainland. Police informed the Immigration Department and asked them to intercept the man if he returned to Hong Kong. The suspect's family co-operated with police and did not tip him off. He was arrested at the Lok Ma Chau border checkpoint when he returned from the mainland on Sunday evening. According to police statistics there had been 40 cases of indecent assault in the Shamshuipo area over the first six months of the year, compared with 36 in the same period last year.