I can't remember the name of an anime?

All I can remember from it is that the people use magic of some kind, but because of that sometimes they turn into these horrible mutant things. So the main character joins up with the police force where they use these giant mechs powered by magic, and they go around killing the mutations. Then the main character figures out that the police chief is behind all of the new monster sightings and he flips out and then turns into a mutant himself I think. Thanks again!