Dressed from head to toe in black, two heavily armed gunmen emerge from their small black Citroen at 11.20am on a chilly and dry Paris day.
One carries a rocket-propelled grenade launcher and both are armed with Kalashnikovs.
A third man is in the car. Having abandoned the vehicle in the middle of the tree-lined street, the pair make their way towards the door of No 6, Rue Nicolas-Appert.
"Is this Charlie Hebdo?" they scream at two unassuming maintenance workers. The men tell them the office of the satirical magazine is two doors down and the gunmen move on, but not before shooting dead one of the workers - the first of their 12 victims.
According to tweets from Yves Cresson, who works for the media production company Bayoo next door, the two attackers initially walked into his office.
"Taking advantage of the postwoman, two armed men wearing balaclavas entered our offices," he tweeted. "They were looking for Charlie."
11.25am: Terror of the young mother and her daughter
Florence Pouvil, a sales assistant who worked opposite the Charlie Hebdo offices, said: "I saw two people with big guns, like Kalashnikovs, outside our office and then we heard firing. We were very confused. There were two guys who came out of the building and shot everywhere. We hid on the floor, we were terrified.
"They came from the building opposite with big guns. We feared for our lives so we hid under our desks so they wouldn't see us. Both men were dressed in black from head to toe and their faces were covered so I didn't see them.
"They were wearing military clothes, it wasn't common clothing, like they were soldiers."
An estate agent said that before entering the building, the attackers approached another man in the street, saying "Tell the media that this is Al Qaeda in Yemen."
Arriving at No 10 - the offices of Charlie Hebdo - the two men approach Corinne Rey, a cartoonist who is arriving at work with her young daughter, having just picked her up from kindergarten.
The gunmen force the terrified woman, also known to her friends as 'Coco', to punch in the four-digit security code allowing them access to the magazine's office. Miss Rey was frogmarched upstairs with her daughter.
The pair hid underneath a desk during the subsequent chaos.
Corinne Rey. Photo / AP
Miss Rey said: "They said they wanted to go up to the offices, so I tapped in the code. They shot on Wolinski, Cabu... it lasted five minutes. I took shelter under a desk. They spoke perfect French. They said they were from Al Qaeda."
11.35am: It's like a butcher's - there are so many dead
Inside the magazine's modern building, on the second floor, reporters and editors are holding their morning news conference.
One witness, who was in an office across the corridor, said she heard "a huge boom".
"Then someone opened the door to our office and asked where Charlie Hebdo was. He had a rifle. We backed away," she said.
Inside the office, the men call out the names of their targets before shooting them dead.
Among those killed were Stephane Charbonnier, 47, the magazine's editor; his police bodyguard; renowned cartoonists Georges Wolinski, 80, Bernard 'Tignous' Verlhac, 57, and Jean Cabut, along with 68-year-old writer Bernard Maris.
Laurent Leger, a Charlie Hebdo writer, managed to sound the alarm and make a phone call at 11.40am. He told a friend: "Call the police. It's carnage, a bloodbath. Everyone is dead." Then the line went dead.
A police source said the two "calm and determined gunmen" went directly up to the editorial room and knew their target.
"It was Charb they were targeting. The two attackers looked for him in the room, shouting, 'Where is Charb? Where is Charb?' They killed him then sprayed everyone else."
Amid the carnage, one journalist texted a friend to say: "I'm alive. There is death all around me. The jihadists spared me."
Others took refuge on the roof, including Benoit Bringer, a journalist whose office is next door. "There were very many people in the building," he said. "We evacuated via the roof just next to the office."
Witnesses said the pair cried "we have avenged the prophet" and "Allahu akbar" (God is greatest) as they left.
Another said: "It's like a butcher's inside there now. There are so many dead."
11.50am: Police arrive on bicycles - then a firefight
The gunmen return to the street - apparently as calmly as they had arrived. From his position on the roof, Mr Bringer said he saw them emerge from the office.
"Three policemen arrived by pushbike," he said, "but they left naturally as the attackers were armed."
The gunmen climb back into their Citroen as more police arrive on the scene and a firefight ensues.
The killers fire at the police car, shooting more than a dozen times. A police spokesman, Rocco Contente, said the men "appeared to have opened fire on everyone".
"It was carnage, absolute butchery."
As they drive away, the gunmen come across another police car in the street. They get out and spray the car with bullets as its wounded driver desperately reverses back up the street.
The reversing police car crashes into a parked car and the wounded officer staggers from his vehicle.
Distressing video footage shows two of the attackers getting out of the vehicle and opening fire on the officer from about 20 yards away. He falls to the floor, his arms out - apparently pleading for mercy.
They advance towards him, rifles on their shoulders. One of the gunmen, who is slightly in front of the other, casually breaks into a jog, and shoots the wounded policeman in the head at close range before walking back to the car shouting: "We have avenged the Prophet Mohammed, we have killed Charlie Hebdo."
One of the gunmen bends down to pick up a shoe before getting in the car, which speeds away.
At the magazine's offices, a man emerges crying. "They are all dead," he says, desperately pleading with bystanders to call the police.
Gerald Kierzec, 40, a casualty doctor on duty at Hotel Dieu, was among the first on the scene.
"I could see this was a military-style attack," he said. "There was a first body lying in the lobby. Then I took the stairs which were covered in blood.
"When I got to the second floor, there were bodies lying one on top of another.
"It was carnage with war wounds. There was blood everywhere.
"These were Kalashnikov injuries with huge bullets that create huge trauma in the victims' faces and chests. They literally explode. As a civilian doctor who deals with car accidents and the like, I have never seen anything like it in my career, so many wounded by gunfire. This was clearly a terror strike."
Some survivors are taken to Hotel Dieu. They were visited by President Francois Hollande, who left in a car with blacked-out windows. Other victims were taken to Pitie Salpetriere, the hospital where Princess Diana died in 1997.
Elsewhere on the street, there was terror.
Fradji Guez said his four-month-old granddaughter Joanne was in the nursery near the Charlie Hebdo offices.
"The staff heard the shooting and were so frightened that they hid the children under the cots," he said. "They were utterly terrified. It's horrific."
12pm: Gunmen steal another car - but spare a dog
Offices of French media, including Le Monde, the country's main newspaper, are put under police protection. The terror alert in France is raised to high.
Driving away at high speed, the Citroen ran down a pedestrian, who is reported to be in a serious condition.
The attackers made it as far as the junction of Rue Sadi-Lecointe and Rue de Meaux, in the 19th Arrondissement, not far from the Place de Stalingrad, before abandoning the damaged car and hijacking another.
A witness said: "They pulled a man, around 60, out of the car behind, a grey Renault Clio. The guy said, 'Wait, let me have my dog!' They let him get his dog before they drove off. The police arrived five minutes later."
4.30pm: Possible hideout searched by police
Anti-terrorist police search a possible hideout used by the attackers. The rented flat is situated in the north-east Paris suburb of Pantin. There were no arrests.
5pm: Thousands gather to mourn the victims
As night falls, thousands start gathering in central Paris in protest and solidarity against the killings.
At the Place De La Republique, mourners lit candles spelling the word 'Charlie'.
One woman said: "It's hard to describe. Wolinski was, well, he was France's cartoonist. It is like someone has come to kill Dali, Picasso - all in one go. They have killed the satire, the 'patrimoine', the heritage. This is one of Paris's saddest days."