Je suis Charlie, which translates to "I am Charlie," started trending on social media as many showed support for the victims of the shooting. The U.S. Embassy in Paris also changed its Twitter profile image to this photo.
This was Charlie Hebdo's cover in 2012 that reemerged on social media in the wake of the shootings.
This video captured the attackers approaching the Charlie Hebdo offices, followed by gunfire.
The video below shows the scene outside the Charlie Hebdo offices.
In 2012, the newspaper printed cartoons that showed a naked Muhammad. In response, the French government shut down schools, embassies and other buildings in "preparation for any retaliation over the cartoons."
"Heard gunshots a while ago," wrote Instagram user andersvinsent. "There was a shooting 1 min from my apartment. Saw a ton of these guys doing their best to safe the situation. Horrible."