When the Benghazi attack began, Gibson’s first duty was to protect the embassy in Tripoli amid fears that it also would be targeted. He helped evacuate the staff to a classified, more secure location.

The United States has arrested and brought to this country a man the government says helped lead the deadly 2012 attack on the U.S. consulate in Benghazi, Libya. Zubayr Al-Bakoush now faces federal ...