A donor of ex-congressman Aaron Schock has filed a lawsuit against the former lawmaker seeking reimbursement of contributions made to his campaign fund.

Schock resigned from his post last month after his use of campaign funds raised eyebrows and sparked calls for an investigation. The U.S. Department of Justice is now probing Schock's use of campaign money and his business dealings following reports of potential illegal use of the funds and questionable deals with donors. Several Schock staffers have been subpoenaed to testify in front of a grand jury about the former congressman's use of campaign funds.

Schock donor Howard Foster, an attorney who donated $500, filed the lawsuit seeking reimbursement for all campaign contributions to the ex-lawmaker and hopes the case will become a class action suit.