A sudden shift in the wind at a critical time of day was all it took to send a wildfire out of control through Fort McMurray, forcing more than 80,000 people out of their homes in what has become the biggest natural disaster in Canadian history.
Earlier this week, Darby Allen, the regional fire chief for the area, minced no words when he was asked what might happen now that more than 1,600 homes have been destroyed.
''This is a really dirty fire,'' he said. ''There are certainly areas within the city which have not been burned, but this fire will look for them and it will take them.''
The media line now is that fire experts saw this coming five years ago when one of the Flattop Complex fires tore through the Alberta town of Slave Lake in 2011, forcing everyone to leave on a moment's notice. A report released shortly after predicted that something similar could happen again, and its authors made 21 recommendations to prepare for the possibility.