In his statement, the prime minister called the shootings a terrorist attack. Prompted by a reporter during a press conference called to react to the shootings, Mulcair agreed that the available facts fit with the definition of terrorism.
Mulcair said it was important for him to come to Ottawa's National Press Theatre to "show solidarity with journalists and all those who defend freedom of speech around the world."
New Democrats stand with the world in condemning this senseless violence, he said.
When news of the attack broke on Wednesday morning, Mulcair said on Twitter he was "shocked and disgusted by the news of a mass shooting in Paris."
"The world mourns with the families of the victims of this senseless violence," his Twitter feed said.
- PHOTOS | Charlie Hebdo offices stormed by masked gunmen
Harper 'angered and saddened'
A statement released Wednesday morning from Harper's office said:
“I am angered and saddened to hear of the terrorist attack today in the offices of the Parisian news magazine “Charlie Hebdo,” which has killed at least 12 individuals, including two police officers.
“On behalf of all Canadians, I offer my deepest condolences to the family and friends of those who lost their lives during this heinous crime and wish a speedy recovery to those injured. The perpetrators of this attack must be apprehended and brought to justice.
“This barbaric act, along with recent attacks in Sydney, Saint-Jean-sur-Richelieu and Ottawa, is a grim reminder that no country is immune to the types of terrorist attacks we have seen elsewhere around the world.
“Canada and its allies will not be intimidated and will continue to stand firmly together against terrorists who would threaten the peace, freedom and democracy our countries so dearly value. Canadians stand with France on this dark day.”