From Brian Ross, etc over at ABC News:
One of the four leaders allegedly behind the al Qaeda plot to blow up a Northwest Airlines passenger jet over Detroit was released by the U.S. from the Guantanamo prison in November 2007, according to American officials and Department of Defense documents. Al Qaeda claimed responsibility for the Northwest bombing in a Monday statement that vowed more attacks on Americans.
American officials agreed to send the terrorist from Guantanamo to Saudi Arabia, where he entered into an "art therapy rehabilitation program" and was set free, according to U.S. and Saudi officials. ABC News described his enrollment in the art therapy program in a January report.
Guantanamo prisoner prisoner #372, Said Ali Shari was sent to Saudi Arabia on Nov. 9, 2007, according to the Defense Department log of detainees who were released from American custody.
The Saudi national has since emerged in leadership roles in Yemen, according to U.S. officials and the men's own statements on al Qaeda propaganda tapes.