The assault on the American consulate in Libya consisted of two separate attacks that forced the Americans from the consulate and then besieged them in a second building in a gunbattle that lasted four and half hours, according to a detailed timeline from a senior administration official.
The bloody offensive by extremists killed Ambassador Christopher Stevens and three other Americans. In addition, three more U.S. personnel were wounded.
Secretary of State Hillary Clinton called the Libyan militants a "small and savage group," and she praised Stevens, who began working in Libya during the revolt against Moammar Gadhafi.
"He risked his life to stop a tyrant and gave his life trying to build a better Libya," she said.
The gunfire erupted around 10 p.m. Tuesday while 25-30 personnel were in the compound which consisted of several buildings and was guarded by a Libyan security force. Libyan Deputy Interior Minister of the Eastern Region Wanis al-Sharif told a news conference today that about 20 gun-wielding attackers fire automatic weapons and rocket-propelled grenades.
By 10:15 p.m., the attackers had stormed the grounds and begun firing on the main building. The U.S. official said that Stevens, 52; Sean Smith, a foreign service information management officer; and a regional security officer were in the main building, which by then had been set ablaze.
By 10:45 p.m., the trio had become separated by thick smoke as they tried to get out of the building. The regional security officer made it out of the building and U.S. security personnel tried to rescue Stevens and Smith. Smith, however, had died of smoke inhalation. His body was pulled from the building.
The searchers were unable to find Stevens before heavy gunfire forced them to retreat to a mission annex building, which was a distance away from the main building.
It took two attempts before American security officials were able to regain control of the consulate at 11:20 p.m., and they evacuated the staff from all of the buildings to the annex.
However, by midnight the U.S. official said today, a second assault began as the annex started taking fire. Libya's al-Sharif said today that a separate group was involved in that firefight. It lasted for more than two hours. Two more personnel were killed in that battle and two were wounded.
By 2:30 a.m., nearly five hours after the assault had begun, Libyan security forces helped to regain control of the site.
The State Department said that some time between 10:15 p.m. and 11:20 p.m., Stevens left the main building and went to the hospital. Clinton said he was taken there by Libyans.
Stevens was not seen by his colleagues until his body was brought later that evening to the Benghazi airport, where all U.S. personnel taken for a flight to Tripoli.
The U.S. official said that all U.S. staff had now been sent to Europe and the wounded are being treated in Germany.
The two other Americans also died during the incident but had not yet been publicly identified, officials said. U.S. officials are still making next of kin notifications.
The attack on the consulate in Benghazi came shortly after protesters in Cairo, Egypt, scaled the walls of the U.S. embassy and tore down the American flag in an angry demonstration against a movie about the life of the Prophet Muhammad, depicting the founder of Islam as a fraud and a womanizer.
Egypt's embassy, along with embassies located in Armenia, Burundi, Kuwait, Sudan, Tunisia and Zambia all issued warnings on Wednesday advising Americans to be particularly vigilant.
Clinton suggested that the movie played a role in the Benghazi attack as well, saying they were "working to determine motivations," but added, "Some have sought to justify this vicious behavior, along with the protest that took place at our embassy in Cairo yesterday, as a response to inflammatory material posted on the Internet."
The secretary of state said she asked herself "how could this happen in a country we helped liberate and in a city we helped to save from destruction." But she added that the people who attacked the consulate were a "small and savage group."
President Obama said in a statement, "I strongly condemn the outrageous attack on our diplomatic facility in Benghazi, which took the lives of four Americans, including Ambassador Chris Stevens. Right now, the American people have the families of those we lost in our thoughts and prayers."
"I have directed my administration to provide all necessary resources to support the security of our personnel in Libya, and to increase security at our diplomatic posts around the globe," the president continued.
Speaking in the White House Rose Garden this morning, Obama said, "We will not waiver in our commitment to see that justice is done for this terrible act. And make no mistake, justice will be done."
Later today Obama issued a statement that as a mark of respect for the memory of Stevens, Smith and the American personnel killed in the attack, the flag of the United States shall be flown at half-staff until sunset on September 16.
Officials have confirmed that 50 marines in the Fleet Antiterrorism Security Team (FAST) are now headed to the embassy in Tripoli from the U.S. Naval Base in Rota, Spain.
A defense official says the bodies have been recovered, though there is still no word on when they might be transported out of the country. All other U.S. personnel at the consulate in Benghazi now have been taken out of the city.
The group suspected of carrying out the consulate attack is called Ansar al Sharia, according to Libyan sources. But the group, which is close to al Qaeda in ideology and is based in east Libya, has denied responsibility for the attack.
Libyan President Mohammed Yussef Magariaf promised to coordinate additional support to protect Americans in the country, condemned the assault on the embassy and pledged his government's full cooperation, Clinton said.
Mohammed el-Megarif, Libya's interim president, apologized to the U.S. on Wednesday for the attack that killed Stevens and vowed to bring the culprits to justice.
Stevens, who was a career member of the Senior Foreign Service and served two tours of duty in Libya, began his term of appointment on May 22, and he was in Libya during the uprising that deposed Qaddafi, serving as the American representative to the transitional national council.
A senior U.S. official told ABC News the State Department is on alert throughout the region and fears there could be more attacks to come.
In Cairo, protesters enraged by the movie scaled the embassy walls and took down the flag from a pole in the courtyard. After trying unsuccessfully to burn it, they ripped it apart and replaced it with a black flag bearing Arabic writing.
The movie was made by Israeli producer Sam Bacile, according to a statement released Wednesday from Afghanistan President Hamid Karzai, and has been promoted by controversial pastor Terry Jones, the Florida preacher whose Koran burning in March 2010 led to the deadly violence in Afghanistan.
Jones said Tuesday in a statement that the movie was titled "Innocence of Muslims" and was intended not to attack Muslims but to show the "destructive ideology of Islam."
"The movie further reveals in a satirical fashion the life of Muhammad," he said.
Afghan President Hamid Karzai issued a statement condemning the movie and called it an "insult" to Islam.
"Desecration is not a part of the freedom of expression, but a criminal act that has now badly affected the righteous sentiments of 1.5 billion Muslims all over the globe," Karzai said.
ABC News' Martha Raddatz and The Associated Press contributed to this report.