The stairways inside the Charlie Hebdo offices “were full of blood” after gunmen stormed the building in a rampage that left 12 dead and 11 others injured, according to one man who arrived on the scene as the shooters were running away.

Paul Moreira is a documentary filmmaker whose studio is mere metres from the office that is home to the satirical newspaper that was targeted by three gunmen Wednesday, reportedly in retaliation for its cartoons depicting the Prophet Muhammad.

Moreira was not inside the building during the attack, but was alerted by a colleague that there had been a shooting in the corridors. He rushed to the building just as the first emergency responders were arriving on the scene.

“The first thing I saw was the doorman killed on the left side of the building,” Moreira told CP24 on Thursday in a telephone interview from Paris.

“Right after, the stairways were full of blood and I saw my crew bringing down a heavily injured journalist.”

The wounded man was shot in both legs, Moreira said. While he will survive, he may lose one of his legs.

“He was bleeding a lot. The stairways were full of blood.”

Inside the Charlie Hebdo offices, Moreira saw 10 bodies. His colleagues had taken two of the survivors to their office.

“They were shaking,” Moreira said. “And very much shocked by what they went through.”

Charlie Hebdo staff knew their offices were at risk of being attacked, Moreira said, “so in a way it made sense that this was happening, as shocking as it seems.”

But they were puzzled by the breakdown in security for the building, which had been ramped up last summer, he said. A heavy police presence that had been outside the building “disappeared three months ago and we were wondering where they were,” he said.

“So we kind of were angry that everything had not been done to protect our colleagues,” Moreira went on, adding that they are now concerned about follow-up attacks.

“We are scared of what will happen in the weeks and months after.”

Picture of shooter

First known picture of the shooters outside the newspaper Charlie Hebdo in Paris, Wednesday, Jan. 7, 2015. (Twitter)

Mass shooting in Paris

Police and officials arrive at the scene of the shooting in Paris at the newspaper Charlie Hebdo, Wednesday, Jan. 7, 2015. (Mathieu Magnaudeix / Twitter)

Paris police at the scene

Police officers and firemen gather outside the French satirical newspaper Charlie Hebdo's office, in Paris, Wednesday, Jan. 7, 2015. (AP / Thibault Camus)

Security at Eiffel Tower

French soldiers patrol at the Eiffel Tower after a shooting at a French satirical newspaper, in Paris, France, Wednesday, Jan. 7, 2015. (AP / Christophe Ena)