This is truly scandalous. 

The RCMP are not the arbiters of the law.

Why not charge them both? 

Let them give their evidence, and the chips fall where they may. 

If there are reasonable and probable grounds for a charge, since when do police get to decide who's telling the truth, and who should pay for their crime, and who should walk?

Isn't that the role of the Court? 

Did the police discuss this with the prosecutors?