Frederick Hill was subpoenaed by Oversight Committee to appear . The panel says new information on the attack prompted its request for testimony . The terror attack in Oversight Committee killed three Americans . NEW : Oversight Committee hearing set for September 2012 .
Kerry was subpoenaed by House Oversight Committee to appear . The panel says new information on the attack prompted its request for testimony . The terror attack in Benghazi killed four Americans . NEW : Oversight Committee hearing set for June 12 .