French police have named Cherif Kouachi, 32, his brother Said Kouachi, 34, and Hamyd Mourad, 18, as the suspects behind the attack. Police released photos of the two Kouachi brothers and asked the public for help in finding them. A man by the name of Hamyd Mourad surrendered himself to police in Paris, and is currently being questioned by police.
The Kouachi brothers grew up in an orphanage in Rennes, north-west France, the sons of Algerian immigrants. Said, who is reported by Le Figaro newspaper to be married, lived in a housing block in Reims. Cherif trained as a fitness coach, and then moved to Paris where he worked as a pizza delivery man.
Cherif Kouachi was briefly interviewed in a 2005 French television documentary as an aspiring rap musician. In the video, he discuses a mosque he frequented in the Stalingrad district of Paris, where he came under the influence of an Imam named Farid Benyettou.
"Farid told me the writings [of the Koran] gave proof of the benefits of suicide attacks. It's written that it's good to die as a martyr," Kouachi says during the report. He also says he was taught how to use a Kalashnikov.
French Court records show that Kouachi was detained by police in 2005, as he attempted to board a plane bound for Syria. In 2008 he was sentenced to three years in prison, of which he served only 18 months for his role in the "Buttes-Chaumont network" that helped send would-be jihadists to fight for al-Qaeda in Iraq.
Kouachi told the court that the evidence of abuse and torture at the Abu Ghraib prison and the influence of the Imam Benyettou had convinced him to give up rapping in favor of an Islamic, jihadist life.
In 2010, Cherif was named in connection to a plot to help Islamist Smain Ait Ali Belkacem escape from a French prison. Said was also named in that plot, but neither brother was prosecuted due to lack of evidence.
Video filmed outside the satirical newspaper's offices shows the gunmen — police now believe there were three — wearing bullet-proof vests and carrying assault rifles. Their movements during a shoot-out with police suggest they had weapons training.
In videos posted from the scene of the attack, the men can be heard yelling "Allahu Akbar" as they fire their weapons. Warning, graphic images:
French news website 20minutes.fr reported one eyewitness as saying the men shouted as they approached the building: "You say to the media that it was al-Qaeda in Yemen."
Cartoonist Corinne "Coco" Rey told the French newspaper L'Humanite she met the gunmen outside the building, and was forced to let them inside.
"As I arrived in front of the door of the paper's building two hooded and armed men threatened us. They wanted to go inside, " she said. "I entered the code. They fired on [the cartoonists] Wolinski, Cabu ... it lasted five minutes ... I sheltered under a desk ... They spoke perfect French ... [and] claimed to be from al-Qaeda."
Cartoonist Stephane Charbonnier, known as Charb, was listed as "wanted" in the March 2013 issue of al-Qaeda's Inspire magazine.
Other witnesses have confirmed the attackers spoke French fluently, and that they appeared to know their way around the building. They attacked as the newspaper was holding an editorial meeting, with all of the top staff collected in the offices.
In this still, taken from one of the videos shot by a witness at the scene, a gunman can be seen raising a single finger in the air.
The gesture is common among Islamic fighters, who raise the finger to allude to the tawhid, the belief in the oneness of God. The tawhid comprises the first half of the shahada, a daily prayer which confirms, "There is no god but Allah, Muhammad is the messenger of Allah."
Increasingly, Islamic State of Iraq and Syria (ISIS) fighters in Iraq and Syria have featured the single-finger salute in videos. The gesture is also used by other Islamist groups across the Middle East and North Africa.
The salute, however, is normally done with the right hand, as many devout Muslims consider the left hand unclean. In the video, the gunman is raising his left hand.
The gesture is also commonly used by the militaries across the globe to signal to fighters that they should regroup.
Charlie Hebdo regularly used its satirical cartoons to poke fun at all religions. It was their depictions of the Prophet Muhammed, however, that appeared to court the most controversy.
In September 2012, after Charlie Hebdo published cartoons of a naked Muhammad, Charbonnier explained the decision to RTL radio:
"If you start by asking whether or not you have the right or not to draw Muhammad … then the next question is, can you put Muslims in the paper? And then, can you put human beings in the paper?
"In the end, you can't put anything in, and the handful of extremists who are agitating around the world and in France will have won."
Despite there being no public claims of responsibility, ISIS supporters on Twitter took credit for the attack, and threatened that further attacks were forthcoming.
The gunmen who carried out the attack are still at large. No group has taken responsibility, but reports from the scene suggest that an extremist Islamic group was behind the attack.
Jyllands-Posten, the Danish newspaper that in 2005 originally published a Prophet Muhammed cartoon that angered many in the Muslim world, has reportedly stepped up its security.
"Surveillance and the level of security in and around our headquarters in Copenhagen ... has been increased," an internal Jyllands-Posten email said, according to Danish paper Berlingske.
"We are following closely the situation in connection with the attack on Charlie Hebdo in Paris earlier today."
Sheera Frenkel is a cybersecurity correspondent for BuzzFeed News based in San Francisco. She has reported from Israel, Egypt, Jordan and across the Middle East. Her secure PGP fingerprint is 4A53 A35C 06BE 5339 E9B6 D54E 73A6 0F6A E252 A50F
Contact Sheera Frenkel at email@example.com.
Got a confidential tip? Submit it here.