With ruthless precision, two masked al-Qaeda gunmen calmly fire eight shots at an unarmed policeman as a terrorist attack of “indescribable barbarity” nears its end. Moments after this image was taken, the policeman, lying mortally wounded on the pavement of a Parisian boulevard, held up a hand in a plea for mercy. A second later, one terrorist jogged past and shot him in the head without breaking stride, just one more act of brutality in an attack that left 12 dead. Earlier two gunmen armed with automatic rifles stormed the office of the satirical magazine Charlie Hebdo, a target for Islamist terrorists since it printed cartoons of the Prophet Mohammed in 2006 and 2011, and killed cartoonists and satirists whose names were called out as they were shot dead in turn.

“We have avenged the Prophet!” the killers shouted in accentless French as they left the building, having identified themselves as acting on behalf of “al-Qaeda in Yemen”. France’s worst terrorist attack in a generation was also its most meticulously planned; the killers had not only memorised the names of those they wanted to kill, they also planned their getaway well enough to evade the police. A nationwide manhunt is now underway after a raid in Reims proved fruitless. The killers were named in the French media as Said and Chérif Kouachi, brothers aged 34 and 32, and Hamid Mourad, 18. Chérif was reportedly part of an Iraqi jihadist network dismantled in the nearby 19th arrondissement. He was jailed for three years on terror charges in May 2008.