How do dead rising 1 ends

The main ending to the game is Overtime mode. At the end of Overtime Mode, you defeat an army veteran Brock, and escape Willamette with the truth. However it does not show Frank leaving the city, it says that in text. The ending shows Frank West Kneeling on the tank that he fought Brock on, and looks up at the sky yelling... Not quite sure why. But he does get away with the story.