WASHINGTON -- Secretary of State Hillary Clinton got testy on Capitol Hill Wednesday in response to a query from Sen. Ron Johnson (R-Wis.), who called into question her department's accounting of the Sept. 11, 2012, attack in Benghazi, Libya.

Facing expected scrutiny from Republicans during her testimony before the Senate Foreign Relations Committee, Clinton appeared to take exception to Johnson's pointed inquiry into the State Department's initial report that the attack had been mounted spontaneously as a reaction to an anti-Islam YouTube video.

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

Clinton continued, defending the State Department's efforts in the wake of the assault. "Honestly, I will do my best to answer your questions about this, but the fact is people were trying their best in real time to get to the best information," she said.

Earlier in the hearing, Clinton spoke about the aftermath of the attack, her voice cracking as she recalled meeting the families of the four Americans killed, including that of U.S. Ambassador Chris Stevens.

UPDATE: 2:00 p.m. -- Johnson spoke with Milwaukee radio host Charlie Sykes shortly after Clinton's hearing, accusing the secretary of state of evading his question and instead making a "big show" of the exchange.

“It was theatrics,” Johnson told Sykes. “Again, she didn’t want to answer questions so she makes a big show of it.”

Johnson continued, saying that he would have liked to ask more questions and defending himself against suggestions that he might have been "too aggressive" in his cross-examination.

“You only have five minutes, so you can’t let the witness or somebody testifying before you filibuster you," the senator said. "You actually have to -- I try and politely interrupt when I hear enough of an answer and I realize she’s just filibustering. ... I’m not trying to be obnoxious here, I’m just trying to get the answers I believe the American people deserve to hear. It’s been four months.”

More on Clinton's testimony from the Associated Press:

Her testimony focused not only on the attack but the growing threat from extremists in northern Africa, pointing out that Libya was not an isolated incident.

"The Arab revolutions have scrambled power dynamics and shattered security forces across the region," she said. "And instability in Mali has created an expanding safe haven for terrorists who look to extend their influence and plot further attacks of the kind we saw just last week in Algeria."

She said the Obama administration is pressing for a greater understanding of the hostage-taking and rescue effort there that left three Americans dead.

In a packed hearing room, Clinton parried tough questions from Republicans, offering a detailed timeline of events on Sept. 11 and the Obama administration efforts to aid the Americans in Libya while simultaneously dealing with protests in Cairo and other countries.

She also took House Republicans to task for recently stripping $1 billion in security aid from the hurricane relief bill.

In something of a valedictory, Clinton noted her robust itinerary in four years and her work, nearly 1 million miles and 112 countries.

"My faith in our country and our future is stronger than ever. Every time that blue and white airplane carrying the words 'United States of America' touches down in some far-off capital, I feel again the honor it is to represent the world's indispensable nation. And I am confident that, with your help, we will continue to keep the United States safe, strong, and exceptional."

Clinton is the sole witness at back-to-back hearings before the Senate and House foreign policy panels on the September raid.

Clinton had been scheduled to testify before Congress last month, but an illness, a concussion and a blood clot near her brain forced her to postpone her appearance.

Absent from the hearing was Sen. John Kerry, D-Mass., the man tapped to succeed Clinton. His swift Senate confirmation is widely expected. Kerry's confirmation hearing is scheduled for Thursday.

Clinton's testimony was focusing on the Libya attack after more than three months of Republican charges that the Obama administration ignored signs of a deteriorating security situation there and cast an act of terrorism as mere protests over an anti-Muslim video in the heat of a presidential election. Washington officials suspect that militants linked to al-Qaida carried out the attack.

"It's been a cover-up from the beginning," Sen. John McCain, R-Ariz., the newest member of the Senate Foreign Relations Committee, said Tuesday.

Politics play an outsized role in any appearance by Clinton, who sought the Democratic presidential nomination in 2008 and is the subject of constant speculation about a possible bid in 2016. The former first lady and New York senator -- a polarizing figure dogged by controversy -- is about to end her four-year tenure at the State Department with high favorable ratings.

A poll early last month by the Pew Research Center for the People & the Press found 65 percent of Americans held a favorable impression of Clinton, compared with 29 percent unfavorable.

On the panel at the hearing were two possible 2016 Republican presidential candidates -- Florida's Marco Rubio and Kentucky's Rand Paul, also a new member of the committee.

Clinton did little to quiet the presidential chatter earlier this month when she returned to work at the State Department after her illness. On the subject of retirement, she said, "I don't know if that is a word I would use, but certainly stepping off the very fast track for a little while."

With respect to Benghazi, the State Department review singled out the Bureau of Diplomatic Security and the Bureau of Near East Affairs, saying there appeared to be a lack of cooperation and confusion over protection at the mission in Benghazi. The report described a security vacuum in Libya after rebel forces toppled the decades-long regime of strongman Moammar Gadhafi.

The report made 29 recommendations to improve diplomatic security, particularly at high-threat posts.

Asked for the number of State Department employees fired for their handling of Benghazi, State Department spokesman Victoria Nuland said four people were put on administrative leave. They included Eric Boswell, who resigned from the position of assistant secretary of diplomatic security.

But Nuland declined to say if Boswell and the others still are working for the department in some capacity.

CORRECTION: A previous version of this article incorrectly stated that Secretary of State Hillary Clinton said, "Give me a break, Senator Johnson. This whole thing is the biggest fairy tale I've ever seen." The quote has been removed. We regret the error.

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  • A burnt out vehicle sits smoldering in flames after it was set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • A broken window after an attack on the U.S. Consulate by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • The U.S. Consulate after an attack by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A burnt car is seen after an attack on the U.S. Consulate by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Soot and debris spills out of the U.S. Consulate after an attack by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A man looks at documents at the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. The graffiti reads, "no God but God," " God is great," and "Muhammad is the Prophet." (AP Photo/Ibrahim Alaguri)

  • A man walks on the grounds of the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Glass, debris and overturned furniture are strewn inside a room in the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A man walks through a room in the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Libyans walk on the grounds of the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Libyans walk on the grounds of the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A vehicle and the surrounding area are engulfed in flames after it was set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • An armed man waves his rifle as buildings and cars are engulfed in flames after being set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle burns after it was set on fire inside the US consulate compound in Benghazi late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle sits smoldering in flames after being set on fire inside the US consulate compound in Benghazi late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle and surrounding buildings smolder after they were set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • LIBYA CONSULATE

    Map locates Benghazi, Libya, where the U.S. ambassador to Libya and three other Americans were killed in an attack