Police your Planet by Lester Del Rey — Read

There were three men, each with a white circle painted on chest and left arm, talking to Mother Corey when Bruce Gordon came down the rickety steps. He stopped for a second, but there was no sign of trouble. Then the words of the thin man below reached him.

"So we figured when we found the stiffs maybe you'd come back, Mother. Damn good thing we were right. We can sure use that ammunition you found. Now, where's this Gordon fellow?"