WASHINGTON -- Sources say suspects Cherif and Said Kouachi were on U.S. no-fly and terror watch lists, and were well known to French counter-terrorism officials before Wednesday's attack.
Cherif Kouachi's arrest made him the more well-known of the two. But, his older brother -- Said Kouachi -- may actually have stronger ties to al Qaeda terrorists.
U.S. sources say French investigators have evidence Said traveled to Yemen in 2011 and linked up with the terrorist affiliate al Qaeda in the Arabian Peninsula. CBS News has been told Said "spent several months" in Yemen training with the group known as AQAP.
During Said's time in Yemen, AQAP's terror operations were being run by the U.S.-born radical cleric Anwar al-Awlaki.
Awlaki was the inspiration behind Nidal Hassan's massacre at Fort Hood. Awlaki also led the failed attempts to hit the U.S. with bombs smuggled onto jetliners inside underwear and computer printers.
It's not clear if Said had any direct dealings with Awlaki before returning to France in 2011. Awlaki was killed by a U.S. drone strike on September 30th the same year.
Investigators believe Said returned home with the intention of using his training to carry out an attack on a target in France. But, law enforcement officials are struggling to explain the three-year gap between Said's homecoming and the mass shooting at Charlie Hebdo.
Investigators don't know if the brothers carried out the massacre on direct orders from AQAP. It's possible the suspects selected their own target and timing. In either case the attack is one of deadliest linked to al Qaeda in a decade.