The Marine Corps is sending a complement of about 50 Marines to Libya in response to a violent attack that killed four Americans in Benghazi, including the U.S. ambassador to the country.

A Marine "FAST team" – for Fleet Anti-terrorism Security Team – will protect U.S. diplomatic personnel in Libya and is heading there now. Sources at the Department of Defense would not confirm if the FAST team, trained to respond to terrorist incidents and protect U.S. installations, will head to the capitol of Tripoli or the city of Benghazi, where the mob attacked.

There is a Marine FAST team headquartered in Rota, Spain, according to the Marine Corps, but it is not clear if that is the team heading to Libya.

There are two Americans confirmed dead in Libya: U.S. Ambassador Christopher Stevens and a foreign service officer, Sean Smith, a U.S. Air Force veteran. Contrary to early media reports, it does not appear that two Marines were killed alongside Stevens and Smith. A Marine Corps official who would not speak for the record told Danger Room that the Corps did not and currently does not have assets in Benghazi. It is currently unclear who the two other Americans dead in Libya are.

"We will work with the Libyan government to bring to justice the killers who attacked our people," President Barack Obama said on Wednesday morning at the White House.

The violent demonstration in Benghazi assembled, ostensibly in reaction, to an American video criticizing the Prophet Muhammad, around the same time a similar mob in Cairo breached the gates of the U.S. Embassy there. Speaking from Washington on Wednesday morning, Secretary of State Hillary Rodham Clinton said "there is no justification for this," and said the "world will never know a true and lasting peace" as long as people use religion as a pretext for violence.

But Clinton did not back away from U.S. support for the new Libyan government, which arose after an eight-month air and naval war by the U.S. and NATO that deposed the longtime Libyan dictator Moammar Gadhafi. Obama administration officials long cited Gadhafi's promise to go "house to house" in Benghazi killing rebels as prompting them to take military action – and so the mob in that very city came as a shock.

Americans wondered "how could this happen in a country we helped liberate, in a city we helped save?" Clinton said. GOP presidential candidate Mitt Romney called the Obama administration's response to the mobs "disgraceful" after the U.S. embassy in Cairo criticized the anti-Muhammad video ahead of the protests but did not voice support for the filmmaker's freedom of speech.

The FAST teams don't have standing equipment, such as standard-issue weaponry and vehicles, for generic missions. According to the Marine Corps, the rapid-reaction teams get equipped specifically for the tasks they're asked to perform, such as evacuating U.S. personnel from crisis areas. Such teams performed evacuation missions in Liberia in 2003 and Haiti in 2004 – but no one from the Defense Department will confirm at the moment whether the FAST team heading to Libya will be tasked with securing U.S. buildings or evacuating U.S. nationals.

In addition to the Marine FAST team, there are four U.S. Navy destroyers in the eastern Mediterranean at the moment, not far from Libya: the USS Laboon, Jason Dunham, Forrest Sherman and the Cole – the ship famously attacked in Yemen by al-Qaida in 2000 – along with support ships. This is a standard complement of Navy forces in the sea, and as of now, the Navy is not moving ships to Libya in response to the crisis. There are no aircraft carriers in the Mediterranean at present.

"We are increasing security as needed around the world," said Army Lt. Col. Steve Warren, a Pentagon spokesman. Where that security will increase will be assessed on "a case by case" basis. While much remains unclear from Libya, including what specifically will come next, there is a joint Pentagon-State Department-White House briefing scheduled for this afternoon; I will provide updates if and when any additional information is available.