The shocking, targeted killing of UnitedHealthcare CEO Brian Thompson Wednesday struck a nerve on social media, triggering an outpouring of negative experiences with the tangled healthcare system in the U.S. Many people shared searing stories of healthcare denials from health insurers. One person said his mom's scan to check on her stage IV lung cancer was recently denied. In another post, a dad shared the letter UHC sent him denying a wheelchair for his son with cerebral palsy.