3 Suspects Identified In Deadly Attack On Paris Newspaper

French police officials identified three men as suspects in a deadly attack against newspaper offices that killed 12 people and shook the nation on Wednesday.

Two officials named the suspects as Frenchmen Said Kouachi and Cherif Kouachi, who are brothers and 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. A witness of Wednesday's shootings at the offices of weekly satirical newspaper Charlie Hebdo said one of the attackers told onlookers, "You can tell the media that it's al Qaeda in Yemen."

The officials spoke on condition of anonymity because they weren't authorized to publicly discuss the sensitive and ongoing investigation. No arrests have been confirmed in the hunt for the attackers.

CBS News' Elaine Cobbe reports that, according to witnesses, two armed and masked men walked into the headquarters of the Charlie Hebdo magazine and opened fire in the entrance hallway, killing people as they saw them. The gunmen reportedly sought out members of the newspaper's staff by name during the rampage through the 2nd floor office, which lasted between five and 10 minutes, according to witnesses.

It was France's deadliest terrorist attack in half a century.

Shouting "Allahu akbar!" as they fired, the men also spoke fluent, unaccented French in the military-style noon-time attack on Charlie Hebdo, located near Paris' Bastille monument. The publication's depictions of Islam have drawn condemnation and threats before -- it was firebombed in 2011 -- although it also satirized other religions and political figures.

There was no immediate claim of responsibility for the shootings, which also left 11 people wounded -- four of them critically -- and was condemned by world leaders as an attack on freedom of expression. Supporters of the Islamic State of Iraq and Syria (ISIS) praised the attack.

CBS News correspondent Bob Orr reports that U.S. intelligence is working with the French authorities in trying to determine who's behind the attack.

"While it is true that Charlie Hebdo magazine has been the subject of violent extremist threats over the past several years, none has been recent nor can they be immediately linked to this attack," a senior U.S. intelligence official told CBS News. "We are working with our intelligence community and foreign partners in identifying the perpetrators of the attack as well as monitoring for threat reporting that might warn of a subsequent attack."

President Francois Hollande said it was a terrorist act "of exceptional barbarism," adding that other attacks have been thwarted in France in recent weeks. Fears have been running high in France and elsewhere in Europe that jihadis returning from conflicts in Syria and Iraq will stage attacks at home.

Cherif Kouachi was convicted in 2008 of terrorism charges for helping funnel fighters to Iraq's insurgency and sentenced to 18 months in prison.

During Cherif Kouachi's 2008 trial, he told the court, "I really believed in the idea" of fighting the U.S.-led coalition in Iraq. He said he was motivated by his outrage at television images of torture of Iraqi inmates at the U.S. prison at Abu Ghraib.

© 2015 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.