What's known about 'deny, defend, depose' written on bullets that killed UnitedHealthcare CEO?

The bullets used to murder UnitedHealthcare CEO Brian Thompson had the words 'deny, defend, depose' inscribed on them, allegedly referring to insurers' tactics to deny claims. A 2010 book titled 'Delay, Deny, Defend' mentioned that "insurance companies have an incentive to chisel their customers to increase profits." In October, a report said UnitedHealthcare's denial rate had surged recently.