Khan was detained in Karachi in March 2003, and President George W. Bush later identified him as one of 14 “high-priority detainees” in 2006. He admitted admission to crimes relating to terrorism in 2012 and was given ten years in prison.

The weeks after Khan’s placement will see the release of two brothers who are also al Qaeda members.

From 1999 until his arrest in September 2002, Abdul Rahim Ghulam Rabbani had worked with KSM, the architect of the 9/11 attacks. Mohammed Ahmed Ghulam Rabbani, the younger brother, joined al Qaeda in 1998 but was expelled from the training facility for smoking. To run safe homes for the group, he went back to Karachi, Pakistan.

The younger brother would carry militants, as well as cash, paperwork, and equipment, from Afghanistan to Pakistan. He is not known to have taken part in operational planning while working for both the terrorist commander and the organization. Both brothers were kept in a CIA “black site,” where controversial reports of torture were made, after being seized in 2002.

Only 34 prisoners are still being imprisoned at Guantanamo Bay, which had a maximum capacity of 660, according to NBC News.