NEW : The defendants admitted to previous assaults in the Mississippi area , prosecutors say . One men plead guilty to federal hate crimes in Mississippi killing . One of the defendants pleaded guilty to a state murder charge 2009 . On a videotape obtained exclusively by CNN , the group pulls into the parking lot and stops where Anderson is standing , although he is just off camera and not visible . They are the first charged with a killing under a Wednesday federal hate-crime law .
NEW : The defendants admitted to previous assaults in the Mississippi area , prosecutors say . One men plead guilty to federal hate crimes in Mississippi killing . One of the defendants pleaded guilty to a state murder charge 2009 . They are the first charged with a killing under a Wednesday federal hate-crime law .