The cheering was loudest when Mr. Bush , flanked by the two top Americans in Baghdad , Gen. George W. Casey Jr. , the overall military commander , and Ambassador Zalmay Khalilzad , spoke of Saddam Hussein as a '' selfish , brutal leader '' who had humiliated Iraqis and denied them freedom , and when he invoked the bombing strike last week that killed America 's most-wanted man in Iraq , Abu Musab al-Zarqawi . ''