Dr Michael Lim had just sat down with a coffee to do some work on his iPad when he heard a "beast-like" scream coming from a nearby shop at Bedok Mall.
The dental surgeon went to investigate and was confronted by a teenager yelling incoherently and waving a pair of scissors at passers-by, a sight which prompted the 62-year-old to call on his knowledge of krav maga, an Israeli self-defence technique.
Along with four other members of the public, Dr Lim managed to subdue the 18-year-old and disarm him last December - an act of bravery which saw him awarded the Public Spiritedness Award in a ceremony held at Bedok Police Division yesterday.
"I didn't want him to hurt any innocent shoppers," Dr Lim told The Straits Times. "I think everybody should help. No one can do everything, but everyone can do something."
Dr Lim was among eight recipients at the event, which honoured members of the public in and around Bedok who have assisted the police.
They included Mohammed Noh Abdul Sukor, 34, the station manager of Tanah Merah MRT station who helped to stop a criminal escaping in June last year.
He found the man, who had been behind a case of outrage of modesty, being pinned down by two members of the public.
Mr Mohammed Noh treated a cut on the suspect's forehead, but the man tried to escape. However, the station manager had been prepared for this happening and soon managed to pin the suspect against a wall. After talking to him and calming him down, Mr Mohammed Noh alerted the authorities and the man was later jailed for two weeks.
Mr Mohammed Noh said no amount of training can prepare people for such situations, adding that such calculated risks are worth taking when assessed carefully. "You know your own strengths, you know your own limits," he said.
The commander of Bedok Police Division, Assistant Commissioner Tan Tin Wee, congratulated the award winners and emphasised the crucial nature of the "close partnership between the police and the community in the fight against crime".