Firefighters, police officers, and forensics gathered in front of the offices of the French satirical newspaper Charlie Hebdo in Paris on January 7, 2015, after armed gunmen stormed the offices leaving 12 dead. (MARTIN BUREAU/AFP/Getty Images)

Two masked men with Kalashnikov rifles stormed the Paris offices of Charlie Hebdo, the French satirical publication best known for publishing controversial cartoons depicting the Prophet Muhammad, opening fire on the newsroom and killing 12 people this morning. French President Francois Hollande told reporters, “This is a terrorist attack, there is no doubt about it,” the AP reports. It’s the deadliest attack in France in several decades.

“This is the darkest day of the history of the French press,” Reporters Without Borders director Christophe DeLoire told the AP.

Today’s violent attack, described by a police official as “carnage,” has not yet been claimed by any militant group. Current reports say 20 other people were wounded in the attack, four or five critically.

The two gunmen fled the scene by car and are still at large. Security has been heightened throughout the city.

The gunmen were captured on video by witnesses outside the building, the AP reports: “Video images on the website of public broadcaster France Televisions showed two gunmen in black at a crossroads who appeared to fire down one of the streets. A cry of ‘Allahu akbar!’ — Arabic for “God is great”— could be heard among the gunshots.”

Marc Weitzmann’s five-part series, France’s Toxic Hate, offers a useful primer on the context and roots of Islamist violence in France.

Charlie Hebdo has long received criticism for repeatedly satirizing the Prophet Muhammad, and has been targeted with violence before. Its offices were firebombed in 2011 after the publication of a so-called “Shariah” edition of the paper, which featured Muhammad on the cover threatening “100 lashes if you don’t die laughing!”

The paper’s most recent tweet, posted minutes before the attack, was a cartoon lampooning Islamic State leader Abu Bakr al-Baghdadi.

Related: France’s Toxic Hate