On March 31, 2004, Iraqi insurgents in Fallujah ambushed two SUVs, killing the four armed Blackwater contractors inside. Local residents hung the charred bodies above a bridge across the Euphrates. In response, U.S. Marines attacked the city in "Operation Vigilant Resolve", which became the first Battle of Fallujah. In the fall of 2007, a congressional report by the House Oversight Committee found that Blackwater intentionally "delayed and impeded" investigations into the contractors' deaths. The report also acknowledges that members of the now-defunct Iraqi Civil Defense Corps "led the team into the ambush, facilitated blocking positions to prevent the team's escape, and then disappeared." Intelligence reports concluded that Ahmad Hashim Abd al-Isawi was the mastermind behind the attack, and he was captured after a Navy SEAL special operation in 2009. al-Isawi was ultimately handed over to Iraqi authorities for trial and executed by hanging some time before November 2013.