Obama on Libya attacks: 'We will bring their killers to justice' LAS VEGAS -- Speaking at a raucous campaign rally in Las Vegas, President Obama vowed to seek justice for those responsible for killing diplomats in an attack on a U.S. consulate in Libya and issued a stern warning to enemies of the United States. We want to send a message to all around the world who would do us harm. No act of violence will shake the resolve of the United States of America," Obama said to a cheering crowd estimated at 8,000 people. I want to assure you we will bring their killers to justice. Obama spoke hours after his administration confirmed the death of U.S. Ambassador to Libya J. Christopher Stevens and Foreign Service officer Sean Smith. The men were two of four killed after protesters attacked and set fire to the consulate in Benghazi. The mob was reportedly angered by an anti-Islamic film promo circulated on the Internet and made in the U.S. Obama's campaign criticized GOP rival Mitt Romney early Wednesday for politicizing the attack. The president's campaign aides said Obama's remarks in Las Vegas would reflect a more measured tone. "It's our view it's not a day of politics as usual," Obama campaign spokeswoman Jen Psaki told reporters flying west on Air Force One. Aside from Obama's brief remarks at the top of his speech, there was little subdued about the Las Vegas event. The raucous crowd at times drowned out the president and erupted in cheers at his attacks on his GOP rivals" policies on Medicare and taxes. Republicans have accused Obama of failing to provide leadership - Romney running mate Paul D. Ryan said as much Wednesday - and Obama took up leadership as a theme, saying America has work to do domestically and abroad "no matter how hard it seems sometimes. That is what I want to talk to you about here today. We have got work to do overseas. We have also got to do work here at home. We have got to do some work right here in the great state of Nevada. Obama continued blasting the Republicans for their recent national convention, reprising a version of a line from his acceptance speech at the Democratic convention in Charlotte, N.C. Republicans offer no new plans, he said, relying only on tax cuts to remedy the nation's economic ills. "And this is their prescription for everything," Obama said. Tax cuts in good times, tax cuts in bad times. Tax cuts when we're at peace, tax cuts when we're at war. Tax cuts to lose those few extra pounds. Tax cuts to give your love life that extra kick. The White House emphasized that Obama was staying in contact about events in the Middle East and was traveling with a member of his national security team. Before leaving Washington, the president delivered somber remarks in the Rose Garden at the White House and went to the State Department to console employees. Still, with just eight weeks until election day, the campaigning did not stop. From Las Vegas, Obama was headed to Golden, Colo., for a campaign rally Thursday.