Wolinski, Cabut, Charb and Tignous (AFP/Getty Images)

At 11:28 a.m., someone at the magazine tweeted on the Charlie Hebdo Twitter account, posting a cartoon by Philippe Honoré mocking the Islamic State leader Abu Bakr al-Baghdadi.

Just at that moment, a black Citroen C3 sedan appeared on the narrow street outside.

Two men dressed in black got out. Their faces were masked by balaclavas and they held Kalashnikov assault rifles.

They looked for Charlie Hebdo but, unsure of the address, first entered the door at 6 rue Nicolas Appert, not realizing they had the wrong address.

A letter carrier who saw the scene told Libération that the men questioned her about Charlie Hebdo. “They didn't know where it was. They fired a few shots to scare us.”

François Molins, the public prosecutor for Paris, said the men then figured out the right address and burst into the entrance hall at 10 rue Nicolas Appert, a three-storey building shared by several companies.

The gunmen asked two maintenance workers in the hall where Charlie Hebdo was located, then opened fire, killing one of the workers, Frédéric Boisseau.

The shooters then ran into a female Charlie Hebdo cartoonist, Corinne Rey, who was returning to the magazine after picking up her daughter at daycare.

"They spoke flawless French … said they were with al-Qaeda," she recalled later.

According to Le Monde, Ms. Rey tried to lead the men to the wrong floor but they eventually found the unmarked door leading to the Charlie Hebdo office.

In an interview with L’Humanité, Ms. Rey said the men threatened her and her daughter at gunpoint, forcing her to punch in the code that unlocked the door.

Inside, they burst into the conference room. According to witnesses, one asked"Charb?" then fired on Mr. Charbonnier, before calling out the names of other cartoonists and shooting at them.

“They fired on Wolinski, Cabu … it lasted five minutes … I hid under a desk,” Ms. Rey said.

Another Charlie Hebdo staffer, Sigolène Vinson, told RFI that one of the shooters aimed his gun at her but didn't shoot.

“I’m not killing you because you are a woman and we don’t kill women but you have to convert to Islam,” he told her.

The men left after killing 10 people. The dead included Mr. Charbonnier, Mr. Wolinski, Mr. Cabut, Mr. Verlhac, Mr. Honoré, the columnist Elsa Cayat and the economist Bernard Maris, who also had a column in the magazine.

Also killed were Mustapha Ourad, a copy editor of Algerian Kabyle origin, Franck Brinsolaro, a police officer assigned to protect Mr. Charbonnier, and Michel Renaud, a former municipal official from the town of Clermont-Ferrand who was visiting.

The survivors said they heard the gunmen shout “Allahu Akbar” and talk about “avenging The Prophet” as they fired at them.

Gunmen flee the offices of French satirical newspaper Charlie Hebdo in Paris, in this still image taken from amateur video.

The gunmen ran back to their car and turned to the right, onto Allée Verte, where they were blocked by an incoming police patrol car. Witnesses hiding on the building's rooftop saw the two shooters step out of the car, yell “Allahu Akbar” and fire several times at the squad car.

Then, according to Mr. Molins, they fired at a police bicycle patrol before driving away as the outgunned officers retreated.

In a third gunfight, a block away, the men again got out of their cars and exchanged shots with another group of police officers. In a shocking amateur video, the men can be seen running towards Ahmed Merabet, a police officer who lay wounded on the sidewalk, shooting him in the head as he raised one arm to protect himself.

Dr. Pelloux, the physician who has a column in Charlie Hebdo, was still at his meeting with emergency responders, about 600 metres away, when his mobile phone rang.

It was a magazine staffer named Jean-Luc who has escaped the carnage. “Come fast, we need you,” he said.

Dr. Pelloux thought at first that it was a prank but he headed towards Nicolas Appert street with Jean-Pierre Tourtier, chief physician of the Paris fire department.

They were the first responders to arrive and were confronted by a scene of blood-smeared wooden floors, toppled furniture and bullet holes.

Firefighters carry an injured man on a stretcher in front of the Charlie Hebdo offices. (Philippe Dupeyrat/AFP/Getty Images)

“It was horrible, horrible. Many were already gone, because they shot them execution-style. We managed to save others,” Dr. Pelloux later recalled in tearful television interviews.

Mr. Charbonnier’s body was tangled into his chair, leading Dr. Pelloux to believe that the editor was killed as he got up and confronted the assaillants.

As the two doctors began tending after the survivors, the gunmen were driving towards the north of the capital.

On Place du Colonel Fabien, about a 15-minute drive north of the scene of the shooting, the Citroen smashed into another car, a Volkswagen Touran.

The female driver of the Volkswagen said there were three aboard the Citroen.

The Citroen limped away but the gunmen had to abandon it about 700 metres further, on Rue de Meaux. They carjacked a Renault Clio and disappeared as a massive manhunt started.

By the next morning, thousands of law-enforcement and military personnel had been deployed around the capital, looking for two suspects, the brothers Said Kouachi, 34, and Cherif Kouachi, 32.

A third man, 18-year-old, Hamyd Mourad , surrendered to police during the night.

On Thursday morning, a still grieving Dr. Pelloux appeared on television, recounting what had happened the previous morning. “I couldn't save them,” he tearfully said.

He announced that Charlie Hebdo would continue to publish. “Because they won't win,” he said.

“Charb, Cabu, Wolenski, Bernard Maris, Honoré, Elsa, Tignous, Mustapha, the guard who was shot, who was protecting us – they didn't die for nothing. There is no hatred to have against Muslims. Everyone each day has to uphold the values of the republic.”