After being fired in 2009 as the top executive of Willard & Kelsey Solar Group, a Perrysburg start-up that has received millions in state loans, William Mitchell made a decision that he wasn't going to go away quietly. Before the company's chief executive officer left his job, he copied company records onto his computer's external hard drive -- months of financial transactions, banking records, and detailed expense reports showing the firm spent thousands on travel and entertainment, including trips to Detroit Tigers games and Pittsburgh Steelers events. Emails from Mr. Mitchell also show that he took a keen interest in...