As storm clouds loomed, the motorcyclists on the Bukit Timah Expressway (BKE) decided to take cover.
Some stopped on the road shoulder under a flyover to put on their raincoats. Without warning, a van drove into them, said one of the victims, Mr Chin Poh Fatt.
The stationary motorcycles toppled and some of the riders were hurled onto the road. Mr Chin, a Malaysian who works in construction, felt the impact from behind. The van had crashed into a motorcycle which fell on his, pinning him down.
"I was afraid. There was a loud noise when the van hit a motorcycle, which later fell on my leg," the 54-year-old recounted to The Sunday Times in Mandarin.
Mr Chin, whose limbs and back were hurt, survived the accident yesterday afternoon, along with five others who were hurt as well.
But two did not make it. The men, aged 34 and 50, died, said the police.
The 25-year-old van driver, a Singaporean, has been arrested for a rash act causing death. "His driving licence will be suspended with immediate effect. Investigations are ongoing," said the police in a statement yesterday evening.
The incident took place at 3.50pm on the BKE towards Woodlands after the Seletar Expressway exit.
A 1½-minute long clip, which was widely circulated, showed six men lying on the road. One had been flung over the railing along the road and was on the grass patch. Two others were lying on the road, motionless and bleeding.
A silver van with a smashed front and a white motorcycle under it could also be seen in the video.
The van driver appeared unhurt.
Some of the motorcycles had toppled over and looked damaged, with motorcycle parts, such as the seats, strewn along the road.
The police urged the public not to circulate images of the deceased, out of respect for their families.
When The Sunday Times visited the scene at about 6.30pm, the area had been cordoned off by the police. Traffic police investigators were on site.
Relatives of the casualties milled about the site, while other motorcyclists involved spoke to the police.
The Singapore Civil Defence Force said the two men were pronounced dead at the scene.
The six casualties were taken to Khoo Teck Puat Hospital.
There, Mr Chin underwent an X-ray at the emergency room before being wheeled away. He could walk though his limbs hurt, he told The Sunday Times, still clutching his motorcycle helmet.
The incident resulted in the left most lane of the expressway being closed to the public, and caused a traffic jam that cleared five hours later at almost 9pm.
Animal researcher Sabrina Jabbar, 27, was on her way to Malaysia via Woodlands Checkpoint when she was caught in the jam.
She left Golden Mile at 5.30pm and reached the accident site at 6.50pm, where two blue tents shielding the bodies were still standing. It was a "terrifying" scene, she said.
WATCH THE VIDEO
Motorcycle being removed from the accident site http://str.sg/4huR