A shocking video has emerged on social media which shows the execution of a police officer in the Paris shooting near the Charlie Hebdo offices.
The video footage shows a police officer lying on the ground with his hands up after a shot by one of the gunmen before one of them runs up to him and executes him.
The masked men continue to run on after shooting the officer dead with seemingly no remorse for their actions.
The footage has been blurred by IB Times UK for censorship reasons and contains graphic images.
The gunmen entered the offices of the magazine and killed at least 12 people, according to French police officials. Two of those were police officers.
Eyewitness Benoit Bringer told French TV channel Itele: "Two black-hooded men entered the building with Kalashnikovs.
"A few minutes later we heard lots of shots."
Francois Hollande condemned the attack as an act "of exceptional barbarity".
British Prime Minister David Cameron tweeted: "The murders in Paris are sickening. We stand with the French people in the fight against terror and defending the freedom of the press."
The satirical magazine's last tweet was one of the Islamic State's caliph Abu Bakr al-Baghdadi.