in lost season two, why did micheal shoot libby and ana lucia?

Actually, he shot them out of fear since they saw him breaking Ben out and was sure they would tell everyone. :)

At that time the losties had Ben kidnapped and locked in the cellar Mike kidnapped by the others when he want looking for Walt they made a deal with him if he would go back to his camp and set Ben free they would let him and Walt leave the island so he went back and Ana Lucia was the only one in the hatch she had a gun and was planning on killing Ben but couldnt do it so Michael tricked her into giving him the gun and the combanation to the cellar then he shot her so that she couldnt be a witness to what he was about to do Libby just happin to walk in at the wrong time and see Ana dead and Michael holding the Gun so he shot her as well

he only planned to shoot ana lucia, because he did not want her to get in his way of freeing ben (henry) and libby was just an accident, she was in the wrong place at the wrong time.

because he thought they were like traitors or something and he was just going crazy.