How were the live US military officials killed?

US military officials in Iraq say five American marines were killed yesterday in Iraq’s Ambar Province. The five men were hit by a roadside bomb during combat operations in the desert region west of Baghdad. In the same region the bodies of 21 Iraqi men were also found, most of the men were killed with bullets to the head, but three were found decapitated. The men were in civilian clothing and it’s not clear whether they are the Iraqi soldiers who were kidnapped in the region as they were headed to Baghdad on leave. The violence took place in an area where US marines carried out two major operations last month. The area is strategically important because it includes the main road from Damascus Syria to Baghdad.