Months before the 2009 Christmas Day terror plot that unfolded in Detroit, Umar Farouk Abdulmutallab was training in Yemen. At his side, investigators said, was one of the men responsible for the recent attack at a French satirical newspaper: Said Kouachi.
The two were roommates at an Arabic training school where they met Anwar al-Awlaki, a radical American-born cleric and one of the best-known al-Qaida figures who was killed by a U.S. drone strike in 2011.
Andy Arena was the head of the FBI's Detroit office when the Christmas Day attack unfolded.
"Young people went to these language schools in Yemen. They would either radicalize before they got there or radicalize once they were there," Arena said. "It's basically a facilitator for them to get people there, to observe them, to radicalize them, and then send them down the road to operations."
Abdulmutallab wore an explosive in his underwear aboard Northwest Airlines Flight 253, which originated in Amsterdam with nearly 300 people aboard. The bomb didn't detonate, but did start a small fire in his lap.
Abdulmutallab pleaded guilty and was sentenced to life in prison without parole in 2012. He's at a maximum security federal prison in Fremont County, Colorado. Investigators could try to talk to him about Kouachi.
"Would he talk to investigators? Who knows," Arena said.
Kouachi and his brother, Cherif, were killed by police in a gunfight after they attacked the Paris offices of Charlie Hebdo, a magazine with a history of mocking Mohammed, on Jan. 7. Twelve people were killed, including several top editors. The brothers said they were avenging the prophet.
Although the attacks took place at different times, on different continents and with different weapons, Arena said they're very similar when you get down to the basics.
"I think the driving force is the same. They believe this warped view of Islam, they buy into it and they're willing to do anything they can for the cause," Arena said.