President Obama condemned the "cowardly, evil" attack Wednesday on a satirical Paris publication that left at least 12 people dead, offering U.S. support to help bring the terrorists to justice.
"This was an attack on journalists, it's an attack on our free press," Obama said, speaking in the Oval Office before meeting with Secretary of State John Kerry and Vice President Joe Biden. He said "the values that we share with the French people" cannot be silenced.
Obama also spoke by phone with French President Francois Hollande, personally offering his condolences, according to the White House.
Black-clad gunmen shouting "Allahu Akbar!" on Wednesday stormed the Paris offices of the Charlie Hebdo weekly, known for lampooning Islam. They killed 12 and injured as many as 15 before escaping, French officials said. It was France's deadliest postwar terrorist attack.
Two officials, speaking on condition of anonymity, named the suspects to the Associated Press as Frenchmen Said Kouachi and Cherif Kouachi, in their early 30s, as well as 18-year-old Hamyd Mourad, whose nationality wasn't immediately clear.
One of the officials said they were linked to a Yemeni terrorist network.
Cherif Kouachi was convicted in 2008 of terrorism charges for helping funnel fighters to Iraq's insurgency and sentenced to 18 months in prison.
All three remain at large.
U.S. officials are in touch with their French counterparts, though Homeland Security Secretary Jeh Johnson said they don't yet know the "nature" of the attack. He said the government would look at whether there is a need to issue any advisories to media organizations in the U.S.
Obama, meanwhile, condemned the "horrific" attack and said he's directed his administration to "provide any assistance needed to help bring these terrorists to justice."
"France is America's oldest ally, and has stood shoulder to shoulder with the United States in the fight against terrorists who threaten our shared security and the world," Obama said in a statement released shortly after the deadly shooting. "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."
Speaking with Fox News, White House Press Secretary Josh Earnest called the shooting an "act of terror that we condemn in the strongest possible terms."
He said top national security officials at the White House are coordinating with counterparts in France. Earnest said officials are still looking into "who's responsible."
Kerry said the U.S. stands in "solidarity" with France and said such attacks can't kill "freedom of expression." Kerry called the murdered journalists "martyrs of freedom."
The attack stirred calls on Capitol Hill for the U.S. to reassess its own security posture. Sen. Lindsey Graham, R-S.C., warned that U.S. intelligence capabilities are "quickly eroding" and urged the administration to change its interrogation and detention policies.
Lawmakers on both sides of the aisle condemned the violence.
"Our thoughts and prayers are with the people of Paris this morning. This vicious terrorist attack is a reminder that we must always be vigilant against the enemies of freedom," House Speaker John Boehner said.
Rep. Michael McCaul, R-Texas, chairman of the House Homeland Security Committee, said he's "confident the brave men and women of the French law enforcement will capture those responsible for this act of terror." He added: "The United States stands ready to assist our French partners, and we join with them in sending a clear message to extremists: your campaign of terror will be stopped and you will be brought to justice."
As many as three Kalashnikov-toting shooters were being sought following the attack. The targeted publication was known for publishing a 2011 caricature of Prophet Muhammed on its cover and recently tweeted a cartoon of Islamic State leader Abu Bakr al-Baghdadi. Two policemen and several journalists, including the cartoonist behind the weekly publication's provocative images, were among the dead.
"We've avenged the honor of the prophet!" the killers shouted, according to witnesses who spoke to Sky News. Other witnesses said the men shouted "Allahu Akbar," Arabic for "God is great." The gunmen spoke French without any accent, according to Le Monde.
The Associated Press contributed to this report.