A third gun linked to "Operation Fast and Furious" was found at the murder scene of Border Patrol Agent Brian Terry, new documents obtained exclusively by Fox News suggest, contradicting earlier assertions by federal agencies that police found only two weapons tied to the federal government's now infamous gun interdiction scandal. Sources say emails support their contention that the FBI concealed evidence to protect a confidential informant. Sources close to the Terry case say the FBI informant works inside a major Mexican cartel and provided the money to obtain the weapons used to kill Terry. Unlike the two AK-style assault...