He had just shared a "kopi break" with his colleague.
It was the last time Mr Shamin, 26, would see his friend, a fellow construction worker from Bangladesh, alive.
His 28-year-old friend, who was known among the crew as Mr Ronju Ahmmed, was one of two workers killed when the boom of a tower crane at a work site at Coleman Street broke and crashed on the roof of the former City Hall building yesterday morning.
Large concrete slabs used as counterweights for the crane then slid off the machinery, smashing through a freestanding scaffold that had workers on it.
The impact killed a Thai and a Bangladeshi construction worker, a statement from the National Arts Council said.
Four others were injured, two seriously. Preliminary findings by the Ministry of Manpower (MOM) revealed that the crane was lowering an excavator when its boom collapsed.
One man was killed by falling pieces of the concrete slabs, the ministry said. His body was trapped at a height of about five storeys in the scaffolding. The other was struck by the crane's hook assembly at the first level of the work site.
He was pronounced dead when the Singapore Civil Defence Force (SCDF) arrived at the scene at about 11.30am.
The crane was at the former City Hall building, which is undergoing renovations as part of the National Art Gallery.
Following the crash, construction work was immediately halted and workers were told to leave, but more than 200 workers remained to see what had happened.
Mr Shamin told The New Paper that Mr Ronju had been working in Singapore for six years. He added that he did not know that his friend had been killed until he saw Mr Ronju's relative enter the accident site together with police officers. Cried
The relative, who said he was Mr Ronju's nephew, broke into tears when he found out about his uncle's death.