Police are investigating an incident in which a man was caught on camera punching a 60-year-old security supervisor at Roxy Square on Thursday.
A 47-year-old man is assisting with investigations.
The incident, which the police have classified as a case of voluntarily causing hurt, left the victim, Mr Andrew Lim, with a swollen eye, a sprained neck and broken glasses.
Mr Lim's employer, security firm Regal Security, is planning to take legal action against the man who hit him.
Yesterday, Mr Lim told The Straits Times that at around 12.15am on the day of the incident, the man approached a security guard complaining that he was trying to leave the building but could not find an exit.
The guard tried to explain that the main exit was locked as it was late, but the man refused to listen and asked to speak to the supervisor, Mr Lim.
Mr Lim said he tried to tell the man that there were several other exits but the man ignored him. He added that the man began behaving in a threatening manner, standing very close to him.
Mr Lim asked: "Are you trying to hit me?"
According to Mr Lim, the man replied: "Yes, maybe later."
At this point, Mr Lim asked the guard to take a video in case anything happened. The video, which was widely circulated on social media yesterday, shows the man telling Mr Lim to "shut the f*** up", mocking him and laughing at him while ignoring Mr Lim's efforts to show him the exit.
The man eventually followed Mr Lim towards an exit - but as the supervisor walked ahead of him, he stuck out his leg and tripped Mr Lim.
Mr Lim told the man: "Hey, enough." But in the video, the man is seen suddenly punching Mr Lim, knocking him to the ground.
Recounting the incident, Mr Lim said after he fell to the ground, the man tried to run away but the guard who was filming moved to stop him.
According to Mr Lim, the man then tried to hit his colleague but missed. He then fled as the guard called the police.
Calling the man's actions "very uncalled for", Mr Lim said: "I've met drunkards and all, but they were not abusive, not aggressive... I thought he might push me, but not like this."
Mr Lim was later given two days' medical leave and sent for an X-ray examination. He was told that he had to go for a CT scan as an abnormality was detected during the X-ray exam.
Regal Security general manager K. Bhaskaran told ST the man returned to the mall to surrender himself late yesterday afternoon after footage of the incident went viral. Mr Bhaskaran said the man also wanted to apologise for the incident.
The general manager said he has hired a lawyer for Mr Lim and the firm intends to take legal action. Mr Lim said Regal Security will be covering his medical and legal costs.