Following a Texas district attorney's shocking assassination, dozens of FBI agents today joined the investigation while armed guards stood outside the Kaufman County Courthouse, CNN reports. Fears that a white supremacist gang is targeting law enforcement officials spread even to Houston, where the chief prosecutor has gone under 24-hour protection. Authorities are investigating links between the murders of Kaufman County District Attorney Mike McLelland, his assistant prosecutor Mark Hasse, and Colorado prison chief Tom Clements. In other developments: