What became clear is just how close the cathedral came to collapsing.

What happened: A guard who responded to the fire went to the wrong building and found nothing. By the time the guard and a fire security company employee realized the mistake, the fire had been burning for more than 30 minutes.

Fighting the fire: Disadvantaged by their late start, firefighters rushed up the 300 steps to the attic only to be forced to retreat. Finally, a small group was sent directly into the flames in a desperate effort to save the cathedral.

The fallout: A bitter round of finger-pointing continues over who was responsible for allowing the fire to rage unchecked for so long. The questions are at the heart of an investigation by the French authorities that will continue for months.