Secretary of State Hillary Clinton became emotional while testifying before Congress on the September attacks in Libya that killed four Americans.

Clinton's voice broke when she told the Senate Foreign Relations Committee her commitment to the safety of diplomats is more than professional.

"It's personal," she said, describing the sight of the four returning coffins and the grieving families there to receive them.

"I stood next to President Obama as the Marines carried those flag-draped caskets off the plane," she said. "I put my arms around the mothers and fathers, the sisters and brothers, the sons and daughters, and the wives left alone to raise their children."

It was an uncharacteristic display of emotion for Clinton, who is usually collected and reserved in public.

Later, in a heated exchange with Sen. Ron Johnson (R-Ws.)

In a heated exchange with Sen. Ronald H. Johnson (R-Wis.), Clinton pounded the witness table as she strongly defended Susan E. Rice, the U.S. ambassador to the United Nations, against his charge of “purposely misleading the American public” about events leading up to the Benghazi attacks. Rice said in television interviews five days after the attacks that they grew out of a spontaneous protest, rather than a planned terrorist operation.

“Nothing could be further from the truth,” Clinton said of Johnson’s accusation. “The fact is that people were trying in real time to get to the best information.”

Clinton told Johnson he was wrong and that he was missing the point with a narrow focus on the wording of the script Rice used. After his repeated questions on the subject, Clinton asked, "With all due respect, the fact is we had four dead Americans. What difference, at this point, does it make?"

Johnson later told BuzzFeed that he believed Clinton "just decided before she was going to describe emotionally the four dead Americans, the heroes, and use that as her trump card to get out of the questions."

Read more about Clinton's testimony.