PARIS - The youngest suspect identified in Wednesday's mass slaying at the office of a French satirical magazine in Paris has surrendered.
Sources told news agencies that Hamyd Mourad, 18, gave himself up to police after a daylong manhunt for him and two brothers suspected of carrying out the massacre. Details of his surrender were unavailable.
Mourad is from the northeastern French city of Reims, where reports said anti-terrorism police had been carrying out an operation.
The search for the two other suspects — Said Kouachi, 34, and his brother, Cherif, 32, both of Paris — was continuing.
Police identified the suspects after one of them left his identity card in the car used to leave the scene of Wednesday's killings: the Paris headquarters of the satirical weekly paper "Charlie Hebdo."
Police said the shootings left at least 12 people dead. Two of the victims were police officers.
French President Francois Hollande denounced the shootings as a terrorist attack and said France's best defense against such "barbarity" was unity. That unity was later displayed when thousands staged a peaceful protest in Paris in defense of free expression.
Hollande declared Thursday would be a national day of mourning.
Late Wednesday morning, black-hooded gunmen carrying Kalashnikov rifles and a pump-action shotgun stormed the weekly's offices, bursting into an editorial staff meeting and opening fire. Terrorism experts said the gunmen appeared to have carried out their attack methodically.
Among the dead on the "Charlie Hebdo" staff were three cartoonists, including co-founder Jean “Cabu” Cabut and editor-in-chief Stephane “Charb” Charbonnier.
The gunmen said "Allahu akbar" and that they were avenging the Prophet Muhammed, Paris prosecutor Francois Molins told reporters.
After dozens of shots rang out, two assailants were seen calmly leaving the scene in a video. One police officer was seen being shot as he lay wounded.
At least 11 others were injured in the attack, including at least four critically. Police union official Rocco Contento described the scene inside the offices as “carnage.”
There was no immediate claim of responsibility for the killings, but jihadists online had repeatedly warned that "Charlie Hebdo" — well-known for courting controversy with satirical attacks on political and religious leaders and publishing numerous cartoons ridiculing the Prophet Muhammed — would pay for its ridicule.
A police union official said there were fears of further attacks. The government declared the highest state of alert, increasing security at transport hubs, religious sites, media offices and department stores as the search for the assailants got under way.
Hollande addressed the nation on television late Wednesday, saying that "an act of indescribable barbarity has just been committed today in Paris,” but insisting that "no act of barbarity will ever extinguish freedom of the press."
He said several other terror plots had been foiled in recent weeks. "We were being threatened because we are a country of freedom," he said. "And because we are a country of freedom, we will fight against these threats and we will punish the aggressors."
He said, “Today, [the slain journalists] are our heroes. And that is why tomorrow will be a day of national mourning, a decreed day. At 12 o'clock there will be a moment of contemplation in all public services."
France last year reinforced its anti-terrorism laws and was already on alert after calls from Islamist militants to attack its citizens and interests in reprisal for French military strikes on Islamist strongholds in the Middle East and Africa.
Hassen Chalghoumi, imam of the Drancy mosque in the north Paris suburb of Seine-Saint-Denis, said of the attack, "I am extremely angry. These are criminals, barbarians. They have sold their soul to hell. This is not freedom. This is not Islam, and I hope the French will come out united at the end of this."
Chalghoumi said of the gunmen: “We must be firm with them, because they want terror, they want racism, they want to pit people against each other.”
The imam of one of France's major cities, Bordeaux, urged Muslims to take to the streets in protest of the Paris attack, calling it "almost an act
of war." Tareq Oubrou said after meeting Pope Francis at the Vatican on Wednesday that the attack on "Charlie Hebdo" was "tantamount to what September 11 meant to America."
Wednesday's public protest in Paris occurred at the Place de la Republique. Agathe Bayeurte was there with her mother, Catherine.