UnitedHealth Group CEO Andrew Witty of UnitedHealthcare sent this message to the major insurer’s employees in the hours after UnitedHealthcare CEO Brian Thompson was shot dead outside a Manhattan hotel on Dec. 4. UnitedHealth Group CEO Andrew Witty of UnitedHealthcare sent this message to the major insurer’s employees in the hours after UnitedHealthcare CEO Brian Thompson was shot dead outside a Manhattan hotel on Dec. 4.