He heard a commotion inside a Sim Lim Square electronics shop, so he went into the ground-floor store to see what was going on.
Tan Peng Wong, 27, saw a man being detained for allegedly stealing earphones.
A shop assistant had tried to detain the man, but he had struggled and challenged the employee to a fight.
When a fellow onlooker took out his mobile phone to film the incident, the alleged shoplifter turned his attention to him and started throwing punches.
Tan, a partner of mobile phone shop "Mackin" on the second floor, and three other onlookers then swung into action, attacking the shoplifter.
For his part in the melee, Tan was yesterday fined $5,000 after pleading guilty to one count of being a member of an unlawful assembly that caused hurt to the alleged shoplifter, Danial Ryan Salleh, 26.
Relating the incident that happened at around 1.30pm on June 29, Deputy Public Prosecutor Krystle Chiang told the court that the shop assistant who tried to detain Danial worked in a store known as Million Tech.
Tan and the onlooker who was attacked by Danial, Mizuta Teruhito, 29, were observing the commotion from a short distance away. Mizuta, a Singapore permanent resident, took out his mobile phone to record the exchange. Noticing this, Danial approached and started punching him.
This escalated into a brawl that was captured by a closed-circuit television camera inside the store.
Other than Tan and Mizuta, the three other men also allegedly involved in the scuffle are Lin Guoming, 28, Yeo Yong Hua, 28, and Gan Guo Rong, 30.
A video clip of the incident was played in court yesterday.
It showed a bare-bodied Danial punching Mizuta before the other onlookers stepped in.
The brawlers bumped against the shelves, causing the displays to fall. Outnumbered, Danial was later seen lying on the floor.
DPP Chiang told District Judge Ng Peng Hong that Yeo and Tan then stopped their assault on him. But Mizuta, Lin and Gan continued punching.
DPP Chiang added: "The assault stopped only after the shop assistant intervened and, together with Tan, pulled the trio away from Danial."
In his mitigation, Tan's lawyer, Mr Peter Fernando, said that his client had merely swung his arms at the alleged shoplifter in a brief two-second period.
He added that the manner in which Tan was involved in the scuffle was "extremely spontaneous and exceptionally brief".
Urging the court to let his client off with a fine, he said: "Tan attempted several times to physically put an end to the fight in a peaceful manner without harming (Danial).
"There are four instances captured on the CCTV recording where he clearly attempted to stop the fight."
Other than Tan, only Mizuta has been dealt with in court for taking part in the scuffle. He was jailed for a month.
The cases involving Lin, Yeo, Gan and Danial are still pending.
For being a member of the unlawful assembly, Tan could have been jailed up to two years and fined.
This article was first published on Nov 6, 2014.
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