Complex sentence: Vern distracts the police, while April and Casey come to retrieve the mutagen, but The Foot arrive ahead of them and in the ensuing battle, the Turtles' existence is revealed to the police, who react with fear and hatred.
Split into simpler sentences: Vern distracts the police, while April and Casey come to retrieve the mutagen, but The Foot arrive ahead of them. In the ensuing battle, the Turtles' existence is revealed to the police, who react with fear and hatred.