WASHINGTON (AP) —Secretary of State Hillary Rodham Clinton, at times emotional and fierce, insisted today that the department is moving swiftly and aggressively to strengthen security at U.S. missions worldwide after the deadly September 11 raid on the consulate in Libya. In her last formal congressional testimony on Capitol Hill as America's top diplomat, Clinton once again took full responsibility for the department's missteps leading up to assault at the U.S. Consulate in Benghazi, Libya that killed Ambassador Chris Stevens and three other Americans. Her voice cracking at one point, Clinton said the experience was highly personal. "I stood next to President Obama as the Marines carried those flag-draped caskets off the plane at Andrews. I put my arms around the mothers and fathers, sisters and brothers, sons and daughters," she told the Senate Foreign Relations Committee at a jam-packed hearing. Her voice rising at another point, she defended U.N. Ambassador Susan Rice, who was vilified for widely debunked claims five days after the attack that protests precipitated the raid rather than terrorism. She challenged the GOP focus on Rice's comments, which were based on intelligence talking points. "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?" said a clearly exasperated Clinton told Sen. Ron Johnson, R-Wis. "It is our job to figure out what happened and do everything we can to prevent it from ever happening again, senator." She insisted that "people were trying in real time to get to the best information," and that her focus was on looking ahead on how to improve security rather than revisiting the talking points and Rice's television appearance. Clinton said the department is implementing the 29 recommendations of an independent review board that harshly criticized the department as well as going above and beyond the proposals, with a special focus on high-threat posts.