PARIS, Jan. 7-- French police on Thursday published photos of two brothers wanted as suspects over a deadly shooting incident at the headquarters of the satirical magazine Charlie Hebdo that killed 12 people.

Paris police said arrest warrants have been issued for Cherif Kouachi, 32, and his 34-year-old brother Said who were "likely armed and dangerous."

A bulletin issued earlier by the French police said they wanted three suspects in connection with the deadly attack, which shocked and angered the French society and triggered a wave of condemnation worldwide.

Local media reported early Thursday that the third suspect, 18-year-old Hamyd Mourad, surrendered to police late Wednesday night in Charleville-Mezieres in the department of Ardennes.

Another source also confirmed that "he was arrested and put in custody."

Several thousand police were deployed Wednesday in France to hunt the hooded gunmen who stormed into the office of magazine Charlie Hebdo and killed 12 people, including eight journalists, two police officers, a maintenance worker and a visitor.

The three perpetrators fled the scene in a black car, an online amateur video showed.

Charlie Hebdo, which is based in Paris' 11th arrondissement, was firebombed in 2011, due to the publishing of a controversial series of cartoons depicting the Prophet Mohammed.

In its last published cartoons, the weekly mocked Abu Bakr al- Baghdadi, leader of the Islamic State, which seized major towns in Iraq and Syria.

An investigation into the deadly shooting is launched by the anti-terrorist section of the office of Paris Prosecutor, head of the office Francois Molins said late Wednesday at a press conference.

In a brief televised speech shortly after the shooting incident, French President Francois Hollande announced Jan. 8 a national day of mourning, and the tri-color national flags will be flying at half mast for three days for those fallen in Charlie Hebdo attack.

The French president said the 12 victims, including 11 men and one woman, were killed "for the idea that they had of France, that's freedom," adding that "Today they are our heroes."

"Our best weapon, it is our unity. Nothing can divide us, nothing can stop us, and nothing can separate us," said the French president, calling on all French citizens to unite at this difficult time.

In a show of solidarity, thousands walked into the streets across the country to mourn the victims and support the freedom of expression.

Political leaders in Europe and beyond were quick to voice condemnations of this deadly attack.

President of the European Council Donald Tusk said the Paris shooting is a "brutal attack against our fundamental values, against freedom of expression which is a pillar of our democracy."

"The fight against terrorism in all its forms must continue unabated," he said.

President of the European Commission Jean-Claude Juncker on Wednesday condemned the shooting in Paris, calling it a "brutal and inhuman" attack.

"This is an intolerable act, a barbarism that challenges us all as human and European beings," Juncker, who is on a trip to Latvia, said in a statement posted on the official website of the EU.

German Chancellor Angela Merkel extended condolences to Hollande, saying she was shocked to learn of the despicable attack.

"I would like to express to you and your compatriots in the hours of suffering the sympathy of the German people as well as my own sorrow, and convey my condolences to the victims' loved ones," Merkel said.

British Prime Minister David Cameron also condemned the attack. "I believe the House will join me in condemning the barbaric attack this morning on an office of a magazine in Paris," he told Westminster. The British government also urged its nationals to take extra care in Paris.

On the other side of the Atlantic, U.S. President Barack Obama and Canadian Prime Minister Stephen Harper, among others, also offered condolences.

Obama called his French counterpart Francois Hollande to offer his condolences over the loss of lives, offering American resources available for help.