WASHINGTON - Four Americans killed in bombings in the Green Zone in Baghdad on Thursday were all employees of the private U.S. security firm DynCorp, a U.S. official said Thursday. Two State Department officials were injured, neither critically, along with another employee of the company, the official said, speaking on the condition of anonymity. The firm, Dyncorp, helps provide security primarily in areas where Americans work in the Iraqi capital. A spokesman for Computer Services Corp., the parent company, had no immediate comment. The fact that insurgents were able to penetrate Baghdad's heavily fortified Green Zone that contained U.S. and...