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,

UnitedHealth Group is facing a class action lawsuit from investors, who allege the company misled them after the December killing of top executive Brian Thompson.

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.

The lawsuit, which seeks class action status, alleges that UnitedHealth and its executives didn’t properly warn investors about how the killing of UnitedHealthcare CEO Brian Thompson would affect its business.

Investors say United HealthCare, the third largest public healthcare company in the world by market value, shifted away from its much maligned practice of denying treatment and claims, without publicly disclosing the impact on company profits.