She went on a one-woman crusade against drugs, even secretly filming an alleged drug dealer in action in Geylang.
She then uploaded the video, titled "ATT: THIS IS HOW THEY (sic) TRADING DRUGS!!!!!", on Facebook and it went viral, garnering over 310,000 views and more than 5,000 shares.
The woman, who was identified only as Ms Tan, told Shin Min Daily News that she carried out the expose because she knew first-hand how damaging drugs are.
While her "vigilantism" may be seen as brave, it was also dangerous, said former policemen The New Paper spoke to.
Ms Tan, 29, who claimed she has a borderline personality disorder, depression and anxiety, told Shin Min that she became addicted to electronic cigarettes and cough syrup in 2012. She would spend almost half her $1,200 monthly salary on cough syrup.
She said that when she stayed at a relative's home, she rented out the place to people who organised drug parties.
Last year, during a police raid, she was arrested for drug-related activities, having consumed Ecstasy and cough syrup.
She was sentenced to a year's jail.
After her release, she told Shin Min that she swore to bring down drug dealers as drugs were harmful.
On Dec 17, she went to Lorong 14 Geylang, approached an alleged drug dealer and pretended to be a customer, she said.
She claimed she bought three bottles of cough syrup and some nitrazepam tablets for $150 so that she could record footage of the alleged dealer in action.
She uploaded the 1 minute 40 second video on her Facebook page the next day.
"These dealers earn about $20,000 to $30,000 every day and have hurt countless people including me. I cannot let them go on doing so," she told Shin Min.
After her post was put up, she started receiving threatening calls and messages. She later posted on her Facebook page that she has reported the matter to the police.
The threatening calls and messages only showed how dangerous Ms Tan's actions were, said Mr Joseph Tan, 49, founder of Crime Library, a voluntary group that helps track down missing people.
"Even police officers don't go alone to do undercover work. You need organisation and teamwork," said Mr Tan, who was a cop from 1985 to 1991.
He added that Ms Tan could have compromised the work of officers who may have been in the field or were tracking the alleged drug dealer.
Security consultant Davy Chan, 68, said that Ms Tan should not have published the video on her Facebook page.
Mr Chan, who was a policeman for 12 years and was awarded a Police Gallantry Medal in 1976, said: "Her name and her identity are now exposed. You don't know who she may have offended and she may be in danger.
"If it's really a drug dealer (in the video), he's someone who lives on the street and you don't know what he may be capable of doing to you."
Mr Tan and Mr Chan both advised members of the public to go to the authorities if they have information on vice activities.
Mr Tan said: "Policemen are trained to take care of their own safety. So let them do their job."
This article was first published on Dec 23, 2015.
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