Hillary Clinton tore into Donald Trump's tax history, business acumen and trustworthiness Monday as she sought to capitalize on news that the New York real estate mogul may not have paid federal taxes for years â€" one of several revelations that rattled the Republican presidential candidate's campaign, according to AP. Campaigning at a union hall, Clinton cast Trump as a cold-hearted and bungling businessman who "represents the same rigged system that he claims he's going to change." She called for a new law requiring presidential candidates to release their tax returns, something Trump has refused to do. Grinning broadly and gesturing eagerly, Clinton mocked Trump for losing money in the casino industry and claimed he left workers and taxpayers to pick up the bill from his failed enterprises. "He's taken corporate excess and made a business model out of it," she said. "It's Trump first and everyone else last." The Democrat's broadside was her first response to a weekend New York Times report that Trump claimed a loss of nearly $916 million in a single year on his personal income taxes. The Times said the size of the loss could have allowed Trump to avoid owing federal taxes for nearly two decades, an assertion his campaign neither confirmed nor disputed.