Former Secretary of State Hillary Clinton went after Donald Trump Wednesday over his decision not to release his tax returns ahead of the November general election.

While speaking to supporters in Camden County, N.J., Wednesday afternoon, Clinton questioned why Trump doesn’t want to release them, saying “we’re going to find out.” She made the remarks after taking issue Trump’s overall tax plan, saying it was “written by a billionaire for billionaires.” Clinton also mentioned that Trump has been on the “defensive” over his plan in recent days.