UnitedHealth Group announced a dramatic leadership shakeup, with former CEO and current chairman Stephen Hemsley stepping back into the top job following the abrupt resignation of Andrew Witty. The move comes at a time of escalating crises for the healthcare giant — including the recent fatal shooting of Brian Thompson,

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.

UnitedHealth Group CEO Andrew Witty is stepping down immediately from his role for “personal reasons,” the company announced Tuesday. He will be replaced by Stephen Hemsley, the health insurer’s board chairman and former CEO from 2006 to 2017.