An argument broke out between two customers at a Tyrwhitt Road coffee shop in Jalan Besar at about 11pm on June 14 and it escalated into a physical altercation.
Mr Yang, who was at the coffee shop at the time of the incident, told Lianhe Zaobao that the Singha and Chang female promoters apparently had beef with each other because of competition in beer sale.
The drinks stall manager, 51-year-old Chen, said a Chang customer acted out of control after drinking that night and was caught on closed circuit television footage slapping the Singha promoter.
Another customer stepped in to shield the Singha promoter but ended up fighting with the Chang customer, who is believed to have attacked the Singha promoter in defence of the Chang promoter.
"The two beer promoters knew each other, so perhaps this happened because of some personal matters," said Ms Chen.
Both the Chang and Singha promoters even tried to mediate the situation but failed. Tables and chairs in the coffee shop were toppled over during the fight but no other customers were hurt.
The fight lasted for about 30 minutes and stopped only after the police arrived.
Two men aged 58 and 65 are assisting in the investigation.
The Singha promoter was injured and taken to Tan Tock Seng Hospital.
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This article was first published in The New Paper. Permission required for reproduction.