(MCT) — WASHINGTON — Three senior State Department officials resigned under pressure Wednesday after an independent review board determined that they had operational responsibility for “grossly inadequate” security when Islamic militants killed four Americans at the U.S. diplomatic mission in Benghazi, Libya.

At a news conference, retired Adm. Michael G. Mullen, a former chairman of the Joint Chiefs of Staff and a leader of the independent panel, said “senior officials in critical positions of authority and responsibility in Washington demonstrated a lack of leadership and management ability.”