The sales representative had just taken cigarette orders from the iEcon mart and was about to leave when a young man came to him, asking for help.
The two then walked a short distance to a white Toyota six-seater parked at a carpark.
Its front door was open, and a man was slumped in the driver's seat.
His foot was still pressed on the accelerator pedal and the engine was still revving.
Mr Tommy Low and the other man tried to call out to him to wake him, without success.
The man's eyes and mouth were wide open and he showed no signs of breathing.
Mr Low, 38, said he told the other man: "I think this guy is already gone. "But I wasn't sure. I was hoping he was still alive," he told The New Paper on Monday.
The incident happened in Jurong West Avenue 5 at around noon on Monday.
A Singapore Civil Defence Force spokesman said they received a call at 12.18pm and sent an ambulance to the scene. The man was pronounced dead at the scene.
Mr Low said he and the young man, whose name he doesn't know, were questioned by the police.
As he had to continue with work, Mr Low said he left at around 1.30pm.
A police spokesman said they are investigating the unnatural death.
Residents in the area said they heard the loud revving of the car.
One resident, who wanted to be known only as Mr Chin, 61, who lives in nearby Block 725 said the noise started around 11.50am.
Ms Kholifah Parlim Sulnya, a maid working in Block 727, was cooking when she heard the engine noise.
When the din did not stop, Ms Kholifah looked out the window and saw the white Toyota, with its doors closed.
Five minutes later, she looked again and the driver seat's door was open. Another resident of Block 725, who wanted to be known only as Suzy, 29, said she watched the whole incident unfold.
"Until the end, I didn't see any family members. It's a bit sad," she said.
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