The husband and wife thought they had heard gas explosions in the city centre about 3pm (5am AEST). 

“We were probably about two-and-a-half blocks away when the blast went off so we just heard two explosions about 10 seconds after each other and very few of the people around us were alarmed at that stage because we just heard them and couldn’t actually see anything,” Mr Buchanan said. 

“It didn’t seem that loud. 

“Then of course when we got home and actually saw what was on TV, we understood the seriousness of the event.” 

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Related coverage: Bendigo runners’ family, friends in shock

Boston terrorist attack's tiniest victim

Bendigo's Americans in mourning

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The explosions killed three people and injured more than 140, shocking the Boston community and many thousands of marathon runners. The Buchanans crossed the finish line about 30 minutes before the blasts. 

“We probably haven’t had time to reflect just yet on how lucky we perhaps were to escape unscathed,” Mr Buchanan said.

“People just can’t believe that this has actually happened. 

“They’re somewhat disgusted, in a state of shock.

“The chaos and the fear and the concern that people had... and I guess the uncertainty of people who had family and friends in the event and not being able to contact them would have been of grave concern.”

The Buchanans emailed family and close friends in Bendigo who were waking up to the horrific news to say they were safe.

The couple left their hotel for dinner last night and noticed increased tension in the city.

“The thing we noticed perhaps was more police on foot and they’re well-armed, (they) have got these automatic guns,” Mr Buchanan said.

“We don’t feel that our safety’s been compromised, but there’s a higher level of security.”

Mr Buchanan said he wasn’t concerned about a bomb threat before the event and was surprised to hear on TV news that race organisers had checked the 42.2km route with sniffer dogs pre-race.

This year’s Boston Marathon was the first for the Buchanans and their third of the “big six” worldwide marathons, after New York and London.

While yesterday’s events didn’t make them feel unsafe for the rest of their five-week trip in North America, they will reconsider competing at any future international marathons.

“For me and Jenny, personally, it will make us think longer and harder. Whether or not it actually influences our decision, I’m not sure,” Mr Buchanan said. 

“But I think for the Boston Marathon organisers it could have a significant adverse effect on future events.”