PARIS, Jan. 7 (UPI) -- An early-morning shooting in Paris has killed a policewoman and seriously injured a second person the day after 12 people were murdered in the terrorist attack at the office of satirical magazine Charlie Hebdo.
The gunman shot the policewoman at point-blank range, according to a witness. He wore a bullet-proof vest and escaped arrest. Police have not determined whether Thursday's attack is related to the Charlie Hebdo massacre.
Earlier, an 18-year-old man suspected in the attack that killed 12 people at the offices of the satirical magazine turned himself into police.
Hamyd Mourad was identified by French police as being one of three men suspected in the attack that killed 12 people and injured 11 others Wednesday.
Police have made seven arrests in the hunt for the remaining suspects and called on the public's help in searching for two other suspects, brothers Said Kouachi, 34, and Cherif Kouachi, 32, both of Paris.
Late Wednesday into Thursday morning, anti-terrorist police focused their investigation on the town of Reims, France, which is located about 90 miles northeast of Paris.
After shooting several people inside the Charlie Hebdo officers, the attackers, described as commandos, exchanged gunfire with police and then escaped in a getaway car driven by a third person. They were being pursued but eluded police further by hijacking a second car.
Witnesses say the gunmen shouted "we have avenged the Prophet Muhammad" and also carried a rocket-propelled grenade.
Police said the methodical way the attack was carried out suggest the gunmen had military training, according to New York Times reporter Dan Bilefsky, who is in Paris.
Hollande asked for unity in a speech he delivered Wednesday evening and declared that "we'll continue to defend the message of liberty on their name." He called for a national day of mourning on Thursday, journalist José Miguel Sardo reported.
"Freedom will always be stronger than barbarism," Hollande said.
Demonstrations have begun to spread across France in support of Charlie Hebdo.
The Telegraph reports one of the gunmen went to a witness and said "tell the media that this is al-Qaida in Yemen."
"This is a terrorist attack, there is no doubt about it," Hollande said. The security level in the country has been raised to the highest position after the attack, which occurred midday during the magazine's daily editorial meeting. Police protection has been implemented in newspaper offices, museums and shopping centers.
The magazine's editor-in-chief Stephane Charbonnier and three cartoonists, identified by French media as Jean Cabu, 76, Georges Wolinski, 80, Bernard Verlhac and Phillipe Honore, 73, are among the dead, which also includes police officers. Security was increased after new threats were directed at Charlie Hebdo in recent weeks.
Journalists Bernard Maris, Michel Renaud, Mustapha Ourrad and Elsa Cayat, maintenance worker Frederic Boisseau, and police officers Franck Brinsolaro and Merabet Ahmed were also killed.
Charbonnier, 47, was on al-Qaida's "Wanted: Dead Or Alive for Crimes Against Islam" list in 2013.
Charlie Hebdo was criticized for publishing Danish cartoons depicting the Prophet Muhammad and its office was firebombed in November 2011.
The magazine's latest tweet was a cartoon of Abu Bakr al-Baghdadi, the Islamic State leader.
British Prime Minister David Cameron tweeted a response, calling the attack "sickening."
President Barack Obama released a statement condemning the shooting.
The murders in Paris are sickening. We stand with the French people in the fight against terror and defending the freedom of the press.— David Cameron (@David_Cameron) January 7, 2015
"Our thoughts and prayers are with the victims of this terrorist attack and the people of France at this difficult time," the statement says.
Obama said France and Paris "offer the world a timeless example that will endure well beyond the hateful vision of these killers." He said he will provide any assistance needed to "America's oldest ally" to "help bring these terrorists to justice."
Secretary of State John Kerry expressed his condolences to the people of France and said a free press and free expression are core, universal values. He called the slain journalists "martyrs for liberty."
Hollande said "no barbaric act will ever extinguish the freedom of the press."
Clay Calvert, director of the Marion B. Brechner First Amendment Project, said on Twitter that satire, parody and free speech "must prevail against terrorists who would squelch it through murder."
An image with text translating to "I am Charlie" showing solidarity after the attack that is circulating social media was placed as Charlie Hebdo's website, along with a link to a PDF document with the phrase in multiple translations.
Many cartoonists are going online to express their sympathy.