''He’s a cold-blooded murderer behind his badge and we can’t keep him around as town marshal.'' ''You really think Mark has turned killer?'' one of them asked. Rohle, who had appointed himself head of the group, said smoothly, ''This last shooting proves it to me. The marshal gunned down an unarmed man. I think Mark is unbalanced. Killing sometimes gets to be a habit that can’t be stopped. ''We’ll give Mark until sundown to turn in his badge and leave town. If he refuses, well - he’ll get a taste of his own medicine.''