Eyewitnesses have described the carnage and terror that ensued as gunmen forced their way into the office of the French satirical Charlie Hebdo magazine in Paris before shooting dead 12 people.
The dead included the editor, Stephane Charbonnier, three other well-known cartoonists and two police officers.
One of the magazine's illustrators, Corinne Rey, described how she was forced to let the gunmen into the Charlie Hebdo office.
Ms Rey, also known as Coco, told L'Humanite she had just fetched her daughter from a nearby creche when "two armed, masked men brutally threatened us".
"They wanted to go in and go upstairs. I entered the (door) code. They fired at Wolinski, Cabu" in an attack that she said lasted five minutes. She hid under her desk as the attack unfolded.
The gunmen "spoke perfect French" and claimed to belong to al-Qaeda, according to Ms Rey.
Other witnesses described seeing black-hooded and masked gunmen entering the building, armed with Kalashnikov rifles. Some said they heard as many as 50 shots fired in the attack that followed.
One passer-by who witnessed the shootout across the street from the Charlie Hebdo office said the gunmen appeared "extremely well-trained".
The attackers "knew exactly what they had to do and exactly where to shoot", the unnamed witness told the Associated Press news agency.
"While one kept watch and checked that the traffic was good for them, the other one delivered the final coup de grace,'' he said, referring to the moment one of the gunmen shot dead an injured police officer at point-blank range.
"They ran back to the car. The moment they got in, the car drove off almost casually," he continued, "they knew exactly down to the centimetre and even to the second what they had to do."
Another man, who lives near the offices, first mistook the sounds of gunshots for celebrations of Chinese new year. However, he said he soon realised the gravity of the situation when he saw "police officers playing hide-and-seek with the criminals".
"I told my wife, who was standing by the window to hide, because she could have been hit by a stray bullet. At one point I saw people hiding behind a van, I saw people hiding in the subway station, and I gathered something serious was going on."
'Rivers of blood'
One witness told AFP the attack was reminiscent of a scene from a movie: "I saw them leaving and shooting. They were wearing masks. These guys were serious.... At first I thought it was special forces chasing drug traffickers or something."
Some journalists sought refuge on the roof of the building during the assault, from where the first amateur footage of the gunmen was taken.
Wandrille Lanos, a TV reporter who works across the road, was one of the first people to enter the Charlie Hebdo office after the attack.
"As we progressed into the office, we saw that the number of casualties was very high. There was a lot of people dead on the floor, and there was blood everywhere," he told the BBC.
Another journalist from the same office described seeing "bodies on the ground, rivers of blood and people seriously injured", in an interview with Itele.