It took little more than an hour. In that amount of time, the spire had fallen, most of the roof had given way, and that was that.
Notre Dame - the literal and figurative heart of Paris, the point from which all distances in the city are measured and the seemingly eternal backdrop to life in the French capital - was essentially no more.
Granted, the facade was preserved, and the bell towers remain intact. But this is without question a story of loss on an otherwise perfect spring day.
To have lived in Paris in recent years is to be well acquainted with loss and even unspeakable tragedy.
The killing of 12 people in the attack at the satirical newspaper Charlie Hebdo after a morning meeting in January 2015.
The bombings and shootings that claimed 130 lives at the national stadium, the Bataclan concert hall and on random cafe terraces near the Canal Saint-Martin.
The killings of two elderly Jewish women - one hurled from her apartment window.
The omnipresence of armed guards at any site where crowds may gather.
But through all of these nightmares, there has been one constant, collective refrain. This was the comforting reality - or at least the comforting belief - that somehow, through it all, Paris was indestructible. The idea that Paris will always be Paris felt truer nowhere else than in front of Notre Dame.
In his remarks to a grieving nation close to midnight local time, President Emmanuel Macron called the cathedral a metaphor for France.
"Notre Dame is our history, our literature, our imagination," he said. "The place of all our great events, our epidemics, our wars, our liberations, the epicenter of our lives."
This is undeniably the case.
The cathedral, completed in the 14th century, has withstood the test of time and the assault of history.
Notre Dame survived the French Revolution, when revolutionaries smashed its statues of Judean kings under the mistaken view that they were French kings instead.
It survived the Paris Commune in the spring of 1871. And it survived two world wars, including Hitler's foiled plans to raze the city to the ground in 1944.
"Is Paris burning?" This is what Hitler allegedly asked just before Paris was ultimately liberated from Nazi occupation in August of that year.
The answer then - and ever since - has been "never."
But then came today, and the unshakeable bedrock turned out to be far more fragile than anyone could have ever imagined.
We do not yet know what happened, or why. All we know is that much of Notre Dame has vanished. Perhaps it was Marx who said it best: "All that is solid melts into air, all that is holy is profaned."
The scene in front of this burning cathedral was profoundly surreal. Most of all, there was an eerie quiet, almost a reverence.
It was already rush hour and happy hour: Cars were on the roads, and couples were already lingering on cafe terraces. Yet no one seemed to notice the car horns or the clink of the glasses.
Even on the other side of the river, there was the heat, and there was the smoke, yellow and brown and orange and black, billowing into a violent cone overhead. Neither of these made a sound.
The quiet broke every so often - gasps when the spire finally tipped over and fell, the whistles of police officers pushing back the crowds. People did move away, but everyone walked backward, so as not to miss a single moment of a spectacle that was both spellbinding and terrifying.
Many were in silent tears; many others embraced strangers. But in general, thousands gathered because they realised they could do nothing else but catch a final glimpse of the place they had known and loved, a place that Macron immediately promised to rebuild but that can never quite be the same again.
The fate of certain stained-glass windows - kaleidoscopes in the sunlight - remains unknown.
For the moment, no one is reported to have died, and that is a blessing to end an otherwise terrible day.
The challenge now will not be to rebuild the structure but what it represented: the security, the safety, the eternity. It may be only partially possible.
As Victor Hugo wrote in The Hunchback of Notre Dame, a novel inspired by this very cathedral: "Great edifices, like great mountains, are the work of ages."
One woman in the crowd, Fatima Marie, 35, a healthcare worker in Paris, said she felt motivated to come and pay her respects to a burning Notre Dame because she had enjoyed an afternoon there with friends only last weekend, sitting on the steps and taking in the flowers in the garden. She had taken a photo of the fire, she said, but she may not keep it.
"What I think I will keep are the photos from the last week," she said, showing me the gallery of the church's gothic buttresses and gargoyles surrounded by lilac trees in full bloom. "We've lost all that now."