UnitedHealth Group’s stock plunged Thursday morning after a report that the embattled insurance giant was being probed for Medicare fraud. The Department of Justice has been conducting the criminal investigation into whether the company — which pushed out CEO Andrew Witty on Monday — manipulated Medicare Advantage billing practices to improperly increase federal payments by inflating patient risk scores,

Andrew Witty, UnitedHealth Group CEO, abruptly resigned today, six months after UnitedHealthcare CEO Brian Thompson was shot and killed in Manhattan by Luigi Mangione, which sparked a national uproar over health care in America.