In one of her last acts as America’s top diplomat, Secretary of State Hillary Clinton hit back hard Wednesday at fierce Republican criticisms over the deadly Sept. 11, 2012, terrorist attack in Benghazi, Libya. Clinton, delivering long-awaited congressional testimony, alternately choked up, pounded the table in anger, laughed and offered clinical replies while vowing to do her utmost to prevent similar tragedies in the future as she was hammered by combative Republicans.

"You let the consulate become a death trap, and that’s national security malpractice," Rep. Jeff Duncan, R-S.C., said during the afternoon House Foreign Affairs Committee hearing. He asked Clinton to define what taking responsibility for the attack means to her.

"I think I've made that very clear, congressman," Clinton responded testily.

Duncan added that the American people felt misled by the way the administration handled the dissemination of information surrounding the attacks—a comment that had been repeated throughout the day of hearings, which started in the morning when Clinton appeared before the Senate Foreign Relations Committee.

Clinton also faced repeated criticism from some on the House Foreign Affairs Committee for not being interviewed by the Accountability Review Board investigating the attack.

"I think that’s outrageous," Rep. Ileana Ros-Lehtinen, R-Fla., said after questioning why Clinton was not interviewed.

"I was not asked to speak," Clinton responded, adding that she would have been "happy to ... if they thought I was relevant."

Earlier in the day, Clinton said to the Foreign Relations Committee, “For me, this is not just a matter of policy—it’s personal."

Her voice broke as she recalled welcoming home the “flag-draped caskets” of U.S. Ambassador to Libya Chris Stevens and three other Americans killed in the terrorist strike at the compound, and putting her arms around bereaved family members.

And she hit the witness table with her fist several times during a contentious exchange with Republican Sen. Ron Johnson, who accused President Barack Obama’s administration of misleading Americans by initially saying the attack grew out of a protest against an Internet video mocking Islam. There was no such demonstration, as officials later acknowledged. Johnson said, “We were misled.”

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“With all due respect, the fact is we had four dead Americans. Was it because of a protest? Or was it because of guys out for a walk one night who decided they’d go kill some Americans? What difference, at this point, does it make,” Clinton scolded Johnson, raising her voice. “It is our job to figure out what happened and do everything we can to prevent it from ever happening again, Senator.”

And Clinton criticized Congress throughout Wednesday's hearings, calling on lawmakers to authorize department funding—something she said the Senate was capable of when she served as a New York senator—as well as approve new rules that would allow personnel to be fired in the absence of a "breach of duty."

Democrats repeatedly made what they probably considered sly allusions to speculation that Clinton will run for president come 2016. Sen. Robert Menendez predicted, “You will not go gently from the world stage,” and Sen. Barbara Boxer said, “You will be sorely missed—but I, for one, hope not for too long.”

Even some Republicans joined in on 2016 talk.

"I wish you the best in your future endeavors ... mostly," Ohio Republican Rep. Steve Chabot said during the House committee hearing, drawing laughter from Clinton herself and other hearing attendees.

Clinton, whose department has drawn heavy fire over the insufficient security arrangements at the American compound in Benghazi, also praised diplomatic security officials. “I literally trust them with my life," she said during the Senate hearing. And she repeatedly denied being aware of numerous requests for more security in Benghazi. "I didn't see those requests," Clinton added.

Senate committee Republicans seized on that admission. Sen. John McCain, in his first hearing as a member of the panel, drew a chuckle from Clinton when he described her as being "as combative as ever" and an appreciative nod as he declared, "we are proud of you" and underlined "you are viewed with admiration and respect." But the Arizona lawmaker quickly got down to business.

He described Clinton's answers as "not satisfactory to me" and scolded the administration for its evolving explanation about who carried out the attack. Americans "don't deserve false answers," he said. "You oughta have your facts straight."

Republican Sen. Rand Paul, making his maiden appearance, was blunter, charging that the fact that Clinton had not been more personally involved had "cost lives."

Paul said, "Had I been president at the time and I found that you did not read the cables from Benghazi, you did not read the cables from Ambassador Stevens, I would have relieved you of your post. I think it's inexcusable."

Clinton said anew that she accepted responsibility for the tragedy.

The secretary of state also said that American diplomats overseas cannot hide behind higher walls and more armed guards. “Our men and women who serve overseas understand that we accept a level of risk to protect the country we love,” she said. “They represent the best traditions of a bold and generous nation. They cannot work in bunkers and do their jobs.”

She rebuked those who may advocate that the U.S. take a more limited role on the world stage at a time when the “Arab Spring” has sown chaos across North Africa and the Muslim world. “We cannot afford to retreat now,” she said.

“When America is absent, especially from unstable environments, there are consequences," Clinton said. "Extremism takes root, our interests suffer, our security at home is threatened.”

Clinton also appeared to confirm that those behind the attacks have not yet been captured.

“We continue to hunt the terrorists responsible for the attacks in Benghazi and are determined to bring them to justice,” she said during the Senate hearing.

Among Clinton’s more notable—and chilling—other comments: Islamist fighters around the region are now equipped with heavy weapons seized from unsecured Libyan arsenals after the fall of strongman Moammar Gadhafi. Critics of the NATO-led campaign to help rebels topple him had warned of the prospect that his arsenals would fall into extremist hands.

That proliferation is “the source of one of our biggest threats” in the region, Clinton said. The American mission in Benghazi was trying to “track down and find and recover” weapons like missiles that can bring down an airplane, she said. But there is “no doubt," she added, that the extremists who carried out a bloody hostage-taking in Algeria, members of Al-Qaida in the Maghreb (AQIM) in Mali and fighters in Syria all had arms from Libya.

“We just have to do a much better job,” she said.

Clinton also told lawmakers that the U.S. “cannot confirm” claims by Algeria’s government that the hostage-takers had also taken part in the attack on Benghazi. And she warned that some 20 American diplomatic facilities face what she described as a serious threat environment.

The secretary of state had been expected to testify in December, but suffered a concussion in a fall at her home while recovering from a stomach bug, then needed treatment for a blood clot near her brain. She had taken questions from lawmakers on the issue once before, but Republicans complained that she had not shared much information.

Clinton appeared one day before Democratic Sen. John Kerry goes before the Senate Foreign Relations Committee he used to chair for a confirmation hearing to succeed her as secretary of state. Democratic Sen. Menendez, Kerry’s successor, leads both hearings.

The Sept. 11 attack raised new questions about Obama’s handling of the “Arab Spring” uprisings that toppled authoritarian regimes in places like Egypt and Libya. It also triggered a months-long battle over how the administration handled repeated requests from Stevens for more security and then explained the tragedy to the American public.

Most notably, U.N. Ambassador Susan Rice withdrew her name from consideration to be Clinton’s successor in the face of Republican opposition. Rice went on major Sunday news shows one week after the attack in Benghazi and, relying on administration-approved talking points, described it as emerging from a protest against an Internet video that ridicules Islam. There was no such demonstration.

Clinton told the committee on Wednesday that she had not been consulted on the decision to make Rice—who was an expert in neither embassy security issues nor Libya— the official in charge of updating Americans on the tragedy. But she defended Rice. "People have accused Ambassador Rice and the administration of misleading Americans," she noted. "Nothing could be further from the truth."

Some of the anger has fizzled, sapped by contentious congressional hearings and a scathing report commissioned by Clinton that faulted the State Department for its handling of repeated requests from Stevens for more security. That report also refuted media reports that the administration chose not to send in troops that might have been able to save Stevens and his colleagues.

Rachel Rose Hartman contributed to this story.