A picture of French journalists on the roof of Charlie Hebdo's offices sounded the first alarm.
They had taken shelter from three armed men who had just opened fire against their colleagues during the weekly satirical newspaper's editorial committee.
Events unfolded very rapidly from then on. French President François Hollande was very quick on the scene, the terrorist nature of the events was confirmed almost immediately and so was the shocking number of casualties: 12 dead and 11 injured, some critically. The operation appeared to have been prepared in a military style with weapons of war.
What can cartoonists with their pen and paper do against killers with automatic weapons?
The news spread fast, sending tremors through France.
Then the dead were given names, this is probably when the news really sank in.
The cartoonists with the noms de plume Charb, Cabu, Wolinski and Tignous, known to millions in France, had been assassinated, at point blank range.
Cabu and Wolinski, in particular, both in their late 70s, have accompanied generations of French people and made them laugh every week, in many different publications, on radio and on television, for over 50 years.
I heard people unable to finish their sentences, forced to hang up the phone on learning the news -- too moved to speak. I saw shoppers stopping in their tracks, sinking lost onto benches, others in tears when learning the news from a friend's call.
As U.S. Secretary John Kerry later commented, both in French and English, from Washington: France gave democracy to the world and knows better than most the price of Liberty.
The French have been shockingly reminded that Liberté, Egalité, Fraternité -- values they fought hard to see every day on the frontispiece of their schools and public buildings -- are threatened by terrorists. While their identities have not yet been confirmed, France, with the largest Muslim community in the Western world (around 6 million out of a population of 66 million) has always been a prime target for Islamist extremists.
In 1995, Paris reeled from a wave of terrorist attacks by the Algerian GIA, which killed a total of 12 people. In 1986, the Hezbollah had carried another deadly attack, bombing the grand magasin Tati, and killing 8 passers-by. French secret services were notoriously good at preventing such plots and President Hollande today revealed that many planned attacks had been very recently foiled.
There will be a lot of soul searching in the next weeks and months within the French and President Hollande is facing difficult questions and an enormous task.
With the far right of Marine Le Pen blowing the flames of national divisions and blaming immigration for France's many social and economic problems, and the left trying very hard not to stigmatize its Muslim citizens, there is little space left for a robust and calm public debate.
The news that the French writer Michel Houellebecq, is now under police protection, as a result of today's attack on Charlie Hebdo, means that the French Interior ministry takes no chances with terrorism, but it also shows the depth of the malaise at the heart of French society.
Houellebecq's latest novel takes place in 2022 during the presidential elections. After a second round between the far right and a French Islamist, the Islamists are rise to victory with the help of the liberal left -- and France is refounded as an Islamic State.
Today, a French imam called the dead journalists and cartoonists of Charlie Hebdo "martyrs of freedom."
But France may have also discovered the price of its complacency and learned that such Fraternité should never be taken for granted.
Agnès C. Poirier is a French journalist and political analyst who contributes regularly to newspapers, magazines and TV in the UK, U.S., France, Italy. The opinions expressed in this commentary are solely those of the author.