How should my zombie story go?

Okay. So i have a zombie story im writing. For right now, im just planning the story out. The main character is a police officer in the town, and the military comes to take control of the virus that has spread. The military isn't letting anyone in or out of the town, and what should the main characters objective be of the story? Should he try protecting civillians? Should he try and escape the town? Oh, and theres a scene where while in the town he witnesses the cities mayor get dropped off witha group of special forces soldiers and they all see him. Then the soldiers want to hunt him down because they dont want to know that they mayors involved. Maybe the story could be of him trying to run from them?