PARIS — The police organized an enormous manhunt across the Paris region on Wednesday for three suspects they said were involved in a brazen and methodical midday slaughter at a satirical newspaper that had lampooned Islam.
The terrorist attack by masked gunmen on the newspaper, Charlie Hebdo, left 12 people dead — including the top editor, prominent cartoonists and police officers — and was among the deadliest in postwar France. The killers escaped, traumatizing the city and sending shock waves through Europe and beyond.
Officials said late Wednesday that the suspects had been identified and that two were brothers. They were identified as Said and Cherif Kouachi, 32 and 34, and Hamyd Mourad, 18. French news reports said the brothers, known to intelligence services, had been born in Paris, raising the prospect that homegrown Muslim extremists were responsible.
Early Thursday, a spokeswoman for the Paris prosecutor said that Mourad had walked into a police station in Charleville-Mézières, about 145 miles northeast of Paris, and surrendered.
“He introduced himself and was put in custody,” said the spokeswoman, Agnès Thibault-Lecuivre.
The assault threatened to deepen the distrust of France’s large Muslim population, coming at a time when Islamic radicalism has become a central concern of security officials across Europe. Within the space of a few minutes, the assault also crystallized the culture clash between religious extremism and the West’s devotion to free expression. Spontaneous rallies expressing support for Charlie Hebdo sprung up later in the day in Paris, throughout Europe and in Union Square in New York.
Officials and witnesses said at least two gunmen carried out the attack with assault weapons and military-style precision.
President François Hollande of France called it a display of extraordinary “barbarism” that was “without a doubt” an act of terrorism. He declared Thursday a national day of mourning.
He also raised the nationwide terror alert to its highest status, saying several terrorist attacks had been thwarted in recent weeks as security officials here and elsewhere in Europe have grown increasingly wary of the return of young citizens from Syria and Iraq where they went to wage jihad.
French authorities put some schools on lockdown for the day, and added security at houses of worship, news media offices and transportation centers, and conducted random searches on the Paris Metro.
The Paris prosecutor, François Molins, said according to witnesses, the attackers had screamed “Allahu akbar!” or “God is great” during the attack, which the police characterized as a “slaughter.”
Corinne Rey, a cartoonist known as “Coco,” who was at the newspaper office during the attack, told Le Monde that the attackers spoke fluent French and had said they were part of al-Qaida.
An amateur video of the assailants’ subsequent gunfight with the police, showed the men shouting, “We have avenged the Prophet Muhammad. We have killed Charlie Hebdo!” The video, the source of which could not be verified, also showed the gunmen killing a police officer as he lay wounded on a nearby street.
The victims at Charlie Hebdo included some of the country’s most revered and iconoclastic cartoonists. The weekly’s editorial director, Stéphane Charbonnier, had already been receiving light police protection after earlier threats, the police and Molins said. An officer assigned to guard the newspaper’s offices and its top editor was among the victims.
As news of the attack spread, an outpouring of grief mixed with expressions of dismay and demonstrations of solidarity for free speech. By the evening, not far from the site of the attack in the east of Paris, an estimated 35,000 gathered at Place de La République — young and old, and various classes — some chanting, “Charlie! Charlie!” or holding signs reading, “I am Charlie” — the message posted on the newspaper’s website.
Spontaneous vigils of hundreds and thousands formed in other cities around France and elsewhere in Europe.
Molin, the prosecutor, said that two men armed with AK-47 rifles and wearing black masks, had forced their way into the weekly’s offices about 11:30 a.m., firing at people in the lobby, before making their way to the newsroom on the second floor, interrupting a news meeting and firing at the assembled journalists.
The attackers then fled outside, where they clashed three times with police, shooting one officer as he lay on the ground on a nearby street. They then fled in a black Citroen, and headed north on the right bank of Paris. During their escape, prosecutors said, they crashed into another car and injured its female driver, before robbing and abducting a bystander.
Police said the precision with which the assailants handled their weapons suggested that they had received military training. During the attack, which police said lasted a matter of minutes, several journalists hid under their desks or went to hide on the roof, witnesses said.
Meziani Zina, 32, who works at the reception of an employment center across from the building, said she heard several loud shots ringing from the weekly’s headquarters.
One journalist, who was at the weekly during the attack and asked that her name not be used, texted a friend after the shooting: “I’m alive. There is death all around me. Yes, I am there. The jihadists spared me.”
Treasured by many, hated by some, and indiscriminate in its offensiveness, Charlie Hebdo has long reveled in provoking.
In 2011, the office of the weekly was badly damaged by a firebomb after it published a spoof issue “guest edited” by the Prophet Muhammad to salute the victory of an Islamist party in Tunisian elections. It had announced plans to publish a special issue renamed “Charia Hebdo,” a play on the word in French for Shariah law.
Police said the dead included four celebrated cartoonists at the weekly, including Charbonnier, known as “Charb,” Jean Cabut, Georges Wolinski and Bernard Verlhac.
Charbonnier stoked controversy and earned the ire of the Muslim community in 2006, when he republished satirical cartoons of the Prophet Muhammad that had been published in a Danish newspaper, Jyllands-Posten. His last cartoon for Charlie Hebdo featured an armed man who appeared to be a Muslim fighter with a headline that read: “Still no attacks in France. Wait! We have until the end of January to give our best wishes.”
Police said that an abandoned black Citroen with silvered wing-mirrors, used by the gunmen, was later discovered in the 19th arrondissement of Paris.
A senior U.S. counterterrorism official said Wednesday that the U.S. authorities were following the developments in Paris closely, but that they had not yet identified any individuals or groups who might be responsible for the attack.
Michael J. Morell, the former deputy director of the CIA and now a consultant to CBS News, said it was unclear whether the attackers acted on their own or were directed by organized groups. He called the motive of the attackers “absolutely clear: trying to shut down a media organization that lampooned the Prophet Muhammad. So, no doubt in my mind that this is terrorism.”
He added, “What we have to figure out here is the perpetrators and whether they were self-radicalized or whether they were individuals who fought in Syria and Iraq and came back, or whether they were actually directed by ISIS or al-Qaida.”
Dalil Boubakeur, the rector of the Grand Mosque in Paris, one of France’s largest, expressed horror at the assault on Charlie Hebdo. “We are shocked and surprised that something like this could happen in the center of Paris. But where are we?” he was quoted as saying by Europe1, a radio broadcaster.
“We strongly condemn these kinds of acts and we expect the authorities to take the most appropriate measures.” He added: “This is a deafening declaration of war. Times have changed, and we are now entering a new era of confrontation.”
The attack comes as thousands of Europeans have gone to join jihadist groups in Iraq and Syria, further fueling concerns about Islamic radicalism and terrorism being imported. Those concerns have been particularly acute in France where fears have grown that militants are seeking to target French citizens in retaliation for the government’s support for the U.S.-led air campaign against jihad with the Islamic State group in Syria and Iraq.
Last month, Prime Minister Manuel Valls ordered hundreds of additional military personnel onto the streets to beef up security after a series of attacks across France raised alarm about Islamic terror.
In Dijon and Nantes, a total of 23 people were injured when men drove vehicles into crowds, with one of the drivers shouting an Islamic rallying cry. The authorities depicted both drivers as mentally unstable. The attacks came after violence attributed to lone-wolf attackers in London in 2013, in Canada in October and last month in Sydney, Australia.
In September, fighters in Algeria aligned with the Islamic State beheaded Hervé Gourdel, a 55-year-old mountaineering guide from Nice, and released a video documenting the murder. Gourdel was kidnapped after the Islamic State called on its supporters to wage war against Europeans to avenge the airstrikes in Iraq and Syria.
President Barack Obama issued a statement condemning the attack. “Time and again, the French people have stood up for the universal values that generations of our people have defended,” he said. “France, and the great city of Paris where this outrageous attack took place, offer the world a timeless example that will endure well beyond the hateful vision of these killers. We are in touch with French officials, and I have directed my administration to provide any assistance needed to help bring these terrorists to justice.”