He was watching the Boston Marathon from the sidelines when the first explosion went off just around the corner. While others were either paralysed with shock or frantically backing away, Massachusetts Institute of Technology postdoctoral fellow Chen Jiahao, 31, went towards the blast, curious to find out what had caused it.

"It was really loud sound like a canon going off, the whole ground shook, and thought I should go take a look," said the Singaporean in a phone interview with The Straits Times.

"The whole street was full of smoke, there were lots of people running away, lots of glass and people just lying on the road. I was just very confused at first, I had no idea what was going on as I couldn't get a cellphone signal for news, so I wanted to find out more," he added.

He stood there for the next half an hour, watching the chaos unfold before him as people were led away screaming and crying. Policemen streamed in, ambulances screeched to a halt metres away, and bomb disposal squads arrived. Mr Chen was finally ushered away by policemen evacuating the area.

Speaking from his home he said it is only slowly hitting him how close he came to being one of those bodies on the road.

"It's still too soon, I'm still taking it in. I don't think I'll get over how close I was to the explosions, but life will have to go on, we'll see what happens but the plan for tomorrow is still to go to work," said Mr Chen.

"The good thing is people in Boston are very stubborn, so that's going to help in the city's resilience."