The Washington Post reports that U.S. officials suspect Sufian Ben Qumu, an ex-Guantanamo detainee, “played a role in the attack on the American compound in Benghazi, Libya, and are planning to designate the group he leads as a foreign terrorism organization.” Ben Qumu is based in Derna, Libya and runs a branch of Ansar al Sharia headquartered in the city.

U.S. officials have found that some of Ben Qumu’s militiamen from Derna “participated in the attack” and “were in Benghazi before the attack took place on Sept. 11, 2012.”