It takes a special kind of brutality to murder a nation's jesters. At 11.30am yesterday Charlie Hebdo's editorial staff - a loose constellation of mostly freelance lampooners - had gathered to decide what might make their 40,000 readers chuckle this week.
They were considering returning to one of their favourite subjects, the comical absurdities of extremist Islam.
Three gunmen, dressed in black combat fatigues and hoods, burst into the small offices at 10 Rue Nicolas-Appert in the 11th arrondissement. Was the first reaction of the cartoonists and writers to think this must be a joke? The gunmen, according to one witness, "spoke perfect French". They shouted something about al-Qaida and the Prophet Mohammed.
A police protection officer rose to intervene, he was shot down. The three men opened fire with automatic weapons. They kept on firing for five minutes. When they left, 20 members of the Charlie Hebdo team were dead or severely wounded. In no democratic country in the world has there ever been such slaughter of journalists in their own editorial offices.
As the three men returned to the street, they were caught on amateur video footage. In one clip, a gunman shouted "Allahu Akbar" (God is great). In another TV clip, another is heard shouting: "We have killed Charlie Hebdo. We have avenged the Prophet Mohammed."
In November 2011 Charlie Hebdo published a special magazine "edited by the Prophet Mohammed". The offices were firebombed that week.
The three gunmen who came back to finish the job yesterday escaped in a small Citroen. Their route was almost immediately blocked by a police car, patrolling the area as part of a permanent protection for Charlie Hebdo.
Mobile phone pictures taken from surrounding buildings show two of the gunmen jumping out of the car and riddling the police vehicle with bullets. The police retreated. The gunmen escaped. In the next street, they shot another police officer. He lay on the pavement, wounded. Chilling footage shot by a passer-by shows a gunman strolling across the street to shoot him in the head.
The escape car was found in the 19th arrondissement, about a mile away. It appeared to have been involved in an accident. The gunmen are thought to have hijacked another car and crossed the Boulevard Périphérique, the motorway that surrounds Paris. Heading that way they would have rapidly reached Seine-Saint-Denis, the area around the Stade de France. This is one of the most heavily Muslim-populated Parisian suburbs.
A huge police and army operation was under way last night to try to pick up their trail.
France, and the world, are praying they are successful.