How did Frank know whom to shoot?
We the viewers know that when Frank shot the Slater with the scratched face, Frank got the bad Slater, because earlier we had seen Gina scratch the face of the bad Slater. However, at the time of the shooting none of the good guys in the film (including Gina) really knew which Slater Gina had scratched. Also in the dialog right before the shooting I did not hear the bad Slater say anything that would give himself away.
So how did Frank know which Slater to shoot?