Hicks also testified that he was instructed by State Department counsel not to allow himself or the acting deputy chief of mission to be personally interviewed by Rep. Jason Chaffetz, R-Utah, an Oversight Committee member traveling to Libya on a congressional delegation to investigate the attack.
When Hicks provided Chaffetz with a classified briefing that excluded a lawyer from State who did not have high enough security clearance to attend, he was phoned by Cheryl Mills, chief of staff to then-Secretary of State Hillary Clinton.
"A phone call from that senior of a person is, generally speaking, not considered to be good news," Hicks said. "She was upset."
Rep. Darrell Issa, R-Calif., the chairman of the Oversight Committee, said the goal of the hearing was "to get answers because [the victims'] families deserve answers."
"They were promised answers at the highest level when their bodies came home," Issa said. "We want to make certain those promises are kept on behalf of those individuals. We also want to make certain that our government learns the proper lessons from this tragedy so it never happens again and so that the right people are held accountable."
Given that today was the first time Congress has heard from anyone who was on the ground in Libya during the attack, lawmakers pledged that the so-called whistleblowers would be protected from potential retaliation.
"I am glad the whistleblowers are here, and I will do every single thing in my power to protect the whistleblowers," Cummings agreed. "Whistleblowers are important. They are very important."
ABC News' Luis Martinez contributed to this report.