The immediate reaction to the murder of 12 people at a French magazine can only be horror at the savagery, revulsion at the inhumanity and sympathy for the victims and their families. The world has united in defiance of the attempt to silence those journalists. It must remain equally vigilant against over-reaction to the killings. We must not become a shadow of that we despise.

Two men, alleged to be brothers, entered the Paris offices of Charlie Hebdo, a weekly satirical magazine that has skewered all things sacred in France since 1970, on Wednesday, wearing black military fatigues and carrying Kalashnikovs. They killed a security guard working at the entrance to the office, and then separated men from women, called out the names of individuals they were seeking.

Their first target was chief editor Stephane Charbonnier, who was among al-Qaida's "most wanted" Westerners for publishing cartoons that made fun of the Prophet Muhammad. They then shot the victims, shouting "Allahu Akhbar!" and "We have avenged the Prophet Muhammad! We have killed Charlie Hebdo!"