It was a split-second decision about the fate of train passengers bound for Halifax.
Dispatcher Vincent Coleman, in the minutes before the harbour explosion on Dec. 6, 1917, stayed at his post, even though he realized disaster was about to strike.
"He was an ordinary man, a family man, and he just went to work that day never assuming anything special was going to happen," Coleman's granddaughter, Ann Finlayson, said in an interview from her Ottawa home.
She remembers growing up hearing the story of Coleman, who was working as a train dispatcher at the station in the Richmond Depot just before two ships collided in Halifax Harbour.
After realizing the munitions ship Mont-Blanc was going to blow, Coleman sent frantic messages trying to stop a train full of passengers headed for the city. Moments later came word the message was received, but by then it was too late for Coleman to flee the blast.
Not far away, Ann Finlayson's mother Eleanor was in class at school.
"They heard this tremendous bang. And they saw clouds coming up from the harbour. And the teacher said, 'I think, children, we are being attacked: run home.' So they all ran home," she said.
"My mother said the street was on fire, houses were burning and people were running up the Russell Street hill, they were all running. People screaming and yelling."
Widow raising four children
Finlayson's grandmother Frances and her aunt Eileen, a baby at the time, had serious injuries that would take many months to heal. Their house collapsed.
Finlayson's mother and other siblings were sent to live with their grandmother on Edward Street and then with other family members in Pictou.
"She missed her family back in Halifax very much," Finlayson said. "The horrific day that changed not only their lives, but the lives of thousands of people in north-end Halifax."
The family finally reunited a year and a half later. Frances Coleman was now a widow with four children to raise, left with just a few mementoes of her husband.
"She had my grandfather's telegrapher's key and his watch. They were the only two things that was given to her when they found the body," Finlayson said. "They were kept in a very safe place. They were very treasured by my grandmother."
Coleman's final telegraphed message — "Munitions ship on fire. Making for Pier 6. Goodbye" — is now etched in history.
However, historians don't know if Coleman's frantic pleas stopped the train.
"The train was held up at Rockingham station, but it was running late to begin with," said Richard MacMichael, co-ordinator of interpretive programming at the Maritime Museum of the Atlantic. The museum holds many artifacts from the explosion.
"The most important thing to know is even if he didn't stop the train, the messages that he sent out went as far as Truro. And it gave people there a sense that something was wrong in Halifax.
"He's still a hero."
And that is how Ann Finlayson remembers him — an ordinary family man who gave his life on an extraordinary day.