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,

Nearly six months after late UnitedHealthcare CEO, Brian Thompson, was fatally shot, UnitedHealth Group’s CEO, Andrew Witty, stepped down for ‘personal reasons.’

Andrew Witty is stepping down as CEO of health care giant UnitedHealth Group in a surprise transition that follows a period of unprecedented turbulence, including the public killing of a company executive and financial woes that in recent weeks have only intensified.

UnitedHealth Group Chairman Stephen Hemsley is returning to helm the health care conglomerate once again. He will replace Andrew Witty effective immediately.

Managed care companies traded sharply lower on Tuesday after the industry leader, UnitedHealth Group (NYSE:UNH), cited elevated medical costs and withdrew its full-year outlook as it announced the sudden resignation of its CEO,

A group of investors this week filed a proposed class-action lawsuit against UnitedHealth Group, alleging that the company withheld information following the murder of UnitedHealthcare CEO Brian Thompson last December.