French journalist Edouard Perrin was clearing his desk Wednesday morning when a colleague rushed back from a smoke break. Men had entered the building, armed with Kalashnikovs.

"Right then I knew," Perrin said. "They were comingforCharlie."

Perrin had revered the ever-edgy cartoonists of Charlie Hebdo since he was a kid in the 1970s, and even worked for the satirical newspaper as a young writer.

Now he and Charlie's stable of legendaryprovocateursshared a bathroom, with the paper's staff occupying an office directly across the hall from his own in an artsy district at the heart of Paris.

Charlie Hebdo was no ordinary neighbor: The satirical tabloid had moved in after its old office was firebombed the day after publishing an infamous 2011 cover mocking Islam. A steady stream of further irreverence followed, including a tweet early Wednesday lampooning the leader of a radical group of Islamists. Perrin lived with the expectation that another attack could come at any time. As he huddled with terrified colleagues behind doors barricaded with furniture, Perrin could hear the confirmation.

That time had finally come.

"It was shot-by-shot -- ta-ta, ta-ta, ta-ta," he said. "And I remember thinking: They're just executing people."

Those sounds of a massacre-in-progress would prove the opening chorus in an epic and tragic drama that over three days transformed Paris from a city of lights and romance into one ofkillingsand horror. By the time it had ended, three of the city's own sons had taken 17 of their fellow citizens to the grave before themselves falling in a flash of explosions and gunfire.

They left behind a traumatized capital city, and a nation grappling with how to match its revolutionary 18th century ideals -- liberty, equality and fraternity --tomessy and fractious 21st century debates over the limits of free expression, the rights of religious minorities and the poisons of extremist ideology.

France would come face to face with the dangerous inroads of radical thought on a susceptible minority of young Muslims who live as outsiders in their own society.

"You cannot justify what happened over those three days," said Mehdi Bouzid, 32, an imam who knew two of the assailants, brothers Chérif and Said Kouachi. "But you can explain it."

On the chilly morning of last Wednesday, Bouzid was feverishly typing away on an Apple desktop in his townhouse in the Paris suburbs, writing a sermon to deliver at Friday prayers. Only a 40-minute drive from the Eiffel Tower in good traffic, the area is nevertheless a world way. A gritty swath of urban sprawl just north of the city with kebab shops and immigrant-run stores, it is theworldof a Muslim preacher such as Bouzid.

It was also the world of Chérif and Said Kouachi.

Shortly after 11 a.m.onWednesday, as news that the brothers had stormed the offices of a satirical newspaper in Paris rapidly spread, Bouzid'scellphonerang. It was his brother.

"Mehdi, did you see the news!" his brother gasped. "They attacked Charlie Hebdo! There are at least 10 dead, maybe more."

Bouzid, a tall vision in white robes and a thick religious beard, flipped on the television to hear the words he had dreaded. Before the gunmen had taken the lives of some of France's most famous cartoonists, eyewitnesses had heard the two brothers shout, "we have avenged the prophet Muhammad."

Again, they use the prophet's name, he recalls thinking. This is going to be difficult for us. For Muslims.

Two hours later, the news went from bad to worse. Authorities found an identity card in the black Citroën C3 the brothers had abandoned in Paris's 20th arrondissement.Bouzidwas stunned when he heard the name. He quickly picked up his phone and searched the Internet for the amateur video that had captured the brothers, both wearing masks, shootingatapolicemen. The officer is wounded and falls to the ground. One of the brothersthen issuesan order.

"Finish him off."

Bouzidstudied the footage several times before he knew for sure.

"That walk! That voice! It was like a puzzle I finally put together," Bouzid said. "It was Chérif."

For more than a decade, Bouzid had known both men, who occasionally attended his mosque in the northern suburb of Aubervilliers. But he particularly knew Chérif, who, Bouzid said, was once a "beautiful guy" if also a "rudderless" young man who, like his brother, had grown up in an orphanage.Bouzidand Chérif Kouachi had played soccer together, and talked about the nature of their faith. In the mid-2000s, when Chérif voiced his hopes to travel to Iraq to fight against U.S.forcesalongside Islamic militants, Bouzid said he had tried to persuade him to set aside his violent ambitions.

"I said, 'Chérif, you cannot know who you are fighting for if you go,'" Bouzid said. "They will say, 'I am the messenger of Allah.' But who are they really? You cannot know."

"But it was too late," he said. "We had lost him. Their message -- the message [of radical Islam] -- is tempting to those like Chérif," he said. "It promises them a place, acceptance, respect. They do not have that here."

Like the brothers, Bouzid grew up as a French-born Muslim of North African descent, living in a rich tapestry of immigrant diversity that is also a breeding ground of resentment and discontent. Marked by high unemployment and poverty, the northern suburbs are warrens of drab, cement-block housing. In 2005, anger spilled over after two Muslim boysdiedwhenthewere electrocuted in a power plant after trying to evade police and a third boy was injured. That spurred days of riots that saw youths torch cars and attack a police station.

"To the French, we are not French," he said. "I am born here, of Tunisian parents, but I cannot go back because there, they call me French. But here, the French call me 'other.' We do not fit, they do not let us. I feel it. I live here. I work here. It is very difficult for us. Chérif was in the same situation."

Bouzidcalls the spilling of blood last week "unforgivable." And yet, even as he watched France fall into a state of shock, he could understand their rage. He, too, felt outraged by Charlie Hebdo depictions of Muhammad. Even the most artful renderings of the prophet are forbidden in Islam. But one depicted in the newspaperhad showedMuhammad naked, on all fours, genitals in full view and mooning France. They were, he said, images designed with one purpose in mind: "To humiliate."

"But this is France, this is a country of freedom of speech. We have to accept that," he said.

And yet, the Kouachi brothers didn't. It led them on a dark path that took them from the newspaper's offices on Wednesday to a printing plant on Friday in an ancient town 26 miles north, where they found themselves surrounded by police before emerging from a crack in a door to stage a dramatic last stand.

As the drama played out at the printing plant, Paris was on edge. Even with the brothers surrounded by police, reports emerged that the fatal shooting of a police officer on Thursday morning -- initially said to be unrelated -- was actually carried out by an accomplice. And no one knew where he was.

Walking back from lunch, a 26-year-old gas station manager in Paris's Porte de Vincennes neighborhood was having a premonition of danger.

"From the start, it was not a normal day. You could feel it," said the manager, who is known to friends asBiland who declined to give his last name for fear of reprisal. "There was a big storm coming." Bil worried the storm was coming directly to Porte de Vincennes.

Situated at Paris's eastern edge, the elegant, middle-class neighborhood had long been a haven for the city's Jewish population. But it also has substantial Christian and Muslim communities and is considered by residents to be a model of French coexistence during a time of rising anti-Semitism and Islam phobia.

As Bil walked back from lunch, he waved to his friend, 22-year-old Yohan Cohen, an employee at the Hyper Cacher -- a kosher market just across the street from Bil's gas station.

"How you doing?" Cohen called out.

"Doing okay! I'll see you later," Bil answered.

The two young men were good friends.Bil, who is Muslim, knew he could count on Cohen to set aside for him several Dame Blanche cakes -- his favorite kind. Cohen had relied onBiland other local Muslims to protect the store last year amid fears that a pro-Palestinian rally could flip into anti-Semitic violence.

Minutes afterBilpassed the store, he heard several loud bangs and recognized instantly what they meant.

"I knew they were coming for the Jews of the Hyper Cacher," he said.

Peering out from the gas station's office, Bil saw a man wielding a Kalashnikov storm into the market, his rifle blazing.

The gunman was Amedy Coulibaly, who would later acknowledge in a call to a Paris television station that he had killed the police officer on Thursday and had coordinated with the Kouachi brothers "from the beginning."

As shoppers and employees inside the store dove for cover, pedestrians on the street outside froze in panic.

"Here! Come inside!" Bil beckoned from his gas station officetoa pregnant woman who had been caught outside the store as the gunfire erupted.

Police moved in fast, and within minutes the lines had been drawninwhat would become a siege of more than four hours. Inside the store, Coulibaly shot four hostages dead and terrified more than a dozen who remained with threats to resume firing if police dared to advance on the Kouachi brothers' hideout in Dammartin-en-Goele.

Outside, Bil watched as police SWAT teams crept into position and plotted a preemptive assault. It would come at sundown, moments after the Kouachi brothers died in a furious shootout with police. Coulibaly, too, was cut down -- allowing the hostages to scamper to freedom.

It wasn't until nearly 24 hours later that Bil learned the fate of his friend Cohen from a news report.

"He's dead?" saidBil, anguished at the discovery. "I can't believe I'm never going to see him again."

Cohen, Bil said, was the antithesis of his killer: "He didn't care if you were Jewish or black or Muslim. We were all friends together."

The killers, on the other hand, "are crazy. They don't understand religion. They're mistaking everything."

Days after the massacre at Charlie Hebdo, the paper is celebrated the world over as a martyr for free expression. The phrase "Je suis Charlie" -- I am Charlie -- echoes across continents.

The slain editors and cartoonists, who relished the role ofimpolitic court jester, may not have approved, said Perrin, the journalist whose office was across the hall from the paper's.

"It's a symbol. And the last thing they would want is to be a symbol," he said. "These are guys who would have refused the Legion of Honor."

Perrin, a trim and bearded man of 43, was among the first to enter Charlie Hebdo's decimated offices after the Kouachi brothers fled. In the paper's tiny, blood-splattered conference room, he found Charlie Hebdo's leading editors, writers and cartoonists. Some were merely wounded, but most were dead.

Perrin felt for pulses and administered first aid to those who could be saved. He carried one man -- his leg oozing blood, his consciousness fading fast -- downstairs to the ambulances that had begun to speed to the scene.

Among those who could not be helped was the paper's editor, Stephane "Charb" Charbonnier. In the face of persistent threats, Charbonnier had said that he would "rather die standing than live on my knees."

So that is what Perrin will be doing on Sunday -- joining with his countrymen for a vigil in Paris's Place de la Republique that is expected to draw tens of thousands, or more, who will try to bring meaning to France's three days of horror.

The message?

"We're standing," Perrin said. "And that's enough."