Sensing that something was amiss, a young man whipped out his mobile phone.
He managed to capture photos of another man who tried to film him using the toilet from the next toilet stall.
On Tuesday (Nov 2), Instagram user Sheearam posted a story recounting the incident which took place at Clementi Mall on Oct 30.
Sharing the voyeur's photo, the 20-year-old salon assistant wrote: "The guy came in the stall next to mine and he closed the toilet seat and I was wondering why he did not leave the toilet [sic]".
Realising that he was indeed being filmed, Sheearam ran out of the toilet to chase the voyeur and took photos of his face.
Sheearam said that he made a police report and hoped that others would "[see] it and share it everywhere".
"If he is [your] father uncle brother or whoever I hope [you] report him because he definitely has done this to other people and I think it's disgusting and I'm never using the public toilets anymore," he wrote.
The police told AsiaOne on Wednesday that they arrested a 40-year-old man in relation to a case of voyeurism on Oct 30 afternoon.
Police investigations are ongoing.
In June, a 36-year-old man was arrested for voyeurism after he was caught taking an upskirt video of a woman at Compass One.
A passer-by spotted his suspicious behaviour and confronted him in a video that was later posted on Facebook.
claudiatan@asiaone.com