Acting on his instinct that something was amiss, good Samaritan Tung Shue Kiong went out of his way to track down a man, who now stands accused of telling a teenage couple that he was a police officer before allegedly raping the girl.
When Mr Tung, 57, finally found Muhammad Firman Jumali Chew at the Woodlands bus interchange, he demanded several times to see his warrant card.
Firman, a pizza delivery man, finally replied that it was at home. Mr Tung retorted: "Is your warrant card like cardboard, so big that you have to keep it at home?"
Mr Tung's account emerged in the High Court yesterday when the lift technician took the stand on the third day of Firman's trial for rape, sexual assault and impersonating a police officer.
Mr Tung, who has serviced the lifts in the area for 20 years, told the court that, before the incident, he had seen the accused in the neighbourhood "four to five times" - sometimes with a pregnant woman.
At about 5pm on Oct 9, 2013, he had gone to the 12th floor of Block 362 Woodlands Avenue 5 for a break when, at the stairwell, he heard a man say "officer".
Mr Tung looked down and saw Firman and the back of a girl. He said Firman immediately left the stairwell after spotting him.
Testifying in Mandarin, Mr Tung said he found it "weird" that Firman left so hastily, with the girl following him. He went down a few floors to look for him, but could not find the man.
At the ground floor, he saw a nervous-looking teenager, who turned out to be the girl's boyfriend. The couple were both 16 at the time.
The boy told him that a man who identified himself as a policeman had asked for their identity cards, then told him to leave so he could talk to the girl alone.
Mr Tung then remembered what he had seen earlier in the stairwell. Certain that Firman was not a policeman, Mr Tung took the lift back to the 12th floor, but found nothing.
He then checked one staircase of the block while the boy checked the other. When this proved futile, he and the boy split up to search after exchanging phone numbers.
Mr Tung "went up and down" five blocks until he was too tired to continue. "It was quite tough on me."
He sat down to rest and told the boy to call him if the girl turned up. The boy later ran back to tell him that his girlfriend had called to say she was at the interchange.
Together, they went to the interchange. There, he saw Firman standing near a bus queue staring at a girl.
Mr Tung said he immediately walked over to "block" Firman while the girl ran to hug her boyfriend. She was crying.
Mr Tung said he asked Firman where he had taken the girl and for his warrant card, but the man initially ignored him and kept staring at the girl.
Mr Tung told the court that the girl boarded a bus without telling him or the boy what Firman had done to her. Firman was still there when he and the boy left, he said.
Later that evening, the boy called him to say that the girl told him she had been raped.
Mr Tung told him to make a police report and gave the boy permission to pass his phone number to the girl's mother.
That night, the girl's mother called him from Malaysia to say they were on their way back to Singapore to make a police report. He told her she could give his phone number to the police.
In cross-examination, Firman's lawyer Ravinderpal Singh contended that Mr Tung was next to the boy when his client told the teen that he took a walk with the girl and bought her a drink. Mr Tung disagreed.
The trial continues.