Two gunmen opened fire at the headquarters of the satirical magazine Charlie Hebdo in Paris on Wednesday, killing 12 people. The gunmen fled the scene shortly after carrying out the crime.

The attack occurred hours after the magazine tweeted a cartoon of Islamic State (ISIS) leader¬†Abu Bakr al-Baghdadi issuing a New Year’s greeting, with the caption: “And especially, health!”

Ten members of the magazine’s staff, including the editor-in-chief and caricaturist Stephane Charbonnier (who publishes under the pen name Charb) were among the dead, according to police. Two police officers were also reportedly killed. Three people were in critical condition.

Some 3,000 police are now on the streets of Paris searching for the attackers. They have found the car used by the killers, a black Citroen, about four hours after the incident, the Guardian reported. The abandoned car was found in the 19th district in northern Paris, where they reportedly hijacked another car.

French President Francois Hollande arrived on the scene shortly after the shooting, and declared that there was no doubt that it was an act of terrorism. An emergency government meeting was planned.

“This is a terrorist operation against an office that has been threatened several times, which is why it was protected,” Hollande said.¬†The French president added that “several terrorist attacks” were thwarted in recent weeks.

“About a half an hour ago two black-hooded men entered the building with Kalashnikovs (guns),” a witness, Benoit Bringer, told French TV channel iTELE. “A few minutes later we heard lots of shots,” he said, adding that the men were then seen fleeing the building.

Security was reinforced at houses of worship, stores, media offices, and transportation following the attack.

Also, Danish media group JP/Politikens Hus, whose newspaper Jyllands-Posten published cartoons in 2005 depicting the Prophet Mohammed, increased its security level because of the shooting, an internal e-mail showed. Jyllands-Posten’s publishing of the cartoons sparked a wave of protests across the Muslim world in which at least 50 died.