When Mannix and Warren Hoxie are ambushed at the lake and Hoxie is shot, the gun fire sound is from a high powered rifle. Later Mannix finds L.B. who fires a revolver at him. The sound is of a handgun firing. Mannix doesn't appear to recognize the difference in the sounds of the guns and that L.B. could have never shot Hoxie with the revolver at that range so there had to be another shooter.