Complex sentence: After a chase across the studio, he childishly and prematurely celebrates his supposed victory, mocking Jason and telling him that he will never tell the truth, as well as admitting that he stole Jason's story, thinking that he will still get away with it.
Split into simpler sentences: After a chase across the studio, he childishly and prematurely celebrates his supposed victory, mocking Jason and telling him that he will never tell the truth. However, he also admits that he stole Jason's story, thinking that he will still get away with it.