US investigates whether Libya attack was planned to mark 9/11 ← Related Article Visit The Boston Globe Share on Twitter Share on Facebook Comment on this Scroll to top of page esam al-fetori/reuters Demonstrators in Benghazi, Libya, held a sign during a rally a day after an attack on the US consulate there killed four US diplomats. esam al-fetori/reuters Among the dead was Ambassador Christopher Stevens. esam al-fetori/reuters Dozens of people participated in the rally. AP Chris Stevens was the first US ambassador to be killed in the line of duty since 1979. ben curtis/associated PRess Stevens was accompanied by an unidentified security staffer at meetings with opposition leaders in Benghazi on April 11, 2011. alex brandon/associated press President Obama and Secretary of State Hillary Clinton greeted State Department personnel in the courtyard of the State Department. AP An attack on the US consulate in Libya killed ambassador Chris Stevens and three other Americans. AP The attackers used machine guns and rocket-propelled grenades to assault the compound. Reuters The flag at the White House flew at half mast to acknowledge the deaths. afp/getty images An armed man was seen at the US consulate in Benghazi, Libya, Tuesday as buildings and vehicles burned. Ibrahim Alaguri/Associated Press Soot and debris spilled out of the US consulate in Libya after an attack the previous night. Esam Al-Fetori/REUTERS A mob of protesters and gunmen had overwhelmed the consulate, setting fire to it in outrage over a film that ridicules the prophet Mohammed. Chip Somodevilla/Getty Images President Obama vowed the US would ‘‘work with the Libyan government to bring to justice’’ those who killed the Americans in Libya. Charles Dharapak/Associated Press Mitt Romney said the Obama administration had sent “mixed signals” to the world and had initially taken on an apologetic tone. J. Scott Applewhite/Associated Press In a statement, Senator John Kerry said "it is exactly the wrong time to throw political punches." US Embassy Tripoli/Associated Press Hillary Clinton praised Stevens (pictured at right) for his "passion for service, for diplomacy and for the Libyan people." Adel Hana/Associated Press Palestinians burned a US flag Wednesday during a protest against the movie, "Innocence of Muslims." AFP/Getty Images A vehicle was engulfed in flames during the attack at the US consulate in Benghazi, Libya, late Tuesday night. REUTERS The consulate in Benghazi came under rocket attack during protests, a Libyan official said. AFP/GETTY IMAGES Protests also raged at the US Embassy in Cairo Tuesday. AFP/Getty Images Protesters would eventually tear down the US flag in Cairo.