The company has been accused of using algorithms to deny treatments and refusing coverage of nursing care to stroke patients. Those practices may face new scrutiny after law enforcement officials said that the bullet casings found at the site of the killing of the UnitedHealthcare chief executive Brian Thompson on Wednesday appeared to have messages, including the words “deny” and “delay,” written on them. The shooter’s motive and identity still remained unknown on Thursday, and no evidence has emerged that the killer was a UnitedHealthcare customer. While the words “deny” and “delay” have multiple meanings, they could be a reference...