The case came to police attention on October 4 as a school reported that an upskirt photo of one of its female students was uploaded to an online forum.

After investigation, police found that someone had uploaded over 100 clandestine photos focusing on women's lower body parts onto the internet, with about 70 photos involving female students from 15 schools who were dressed in school uniforms.

According to officers, the photos were mostly taken on public transport like buses or MTR trains. Some were taken in a packed area so that the crime would not be easily spotted. The suspect then made money by selling the photos and videos to those in the forum who are interested in the photos.

Officers soon targeted a suspect and mounted an operation on Tuesday afternoon. Cops in plain clothes arrested a 20-year-old man as they caught him tailing a female student on an escalator at Choi Hung MTR station and trying to take upskirt photos of that student.

The arrestee is a jobless man and is not a triad member.

Later officers searched his home at Kin Ming Estate in Tseung Kwan O and found more upskirt photos and videos in his computer, as well as three imitation hand guns and two imitation short guns. Over 9,000 rounds of airsoft pellets were found as well.

The man's 49-year-old mother was also arrested as officers suspect that she is connected to the case. The two were arrested for unlawful recording or observation of intimate parts, theft and possessing imitation firearms.

The investigation is still underway, police noted, adding that they now have information of those who purchased the clandestine photos from the suspect and there may be more arrests to be made.