“Thoughts and prior authorizations!” wrote another user.

“I would be happy to help look for the shooter but vision isn’t covered under my healthcare plan,” one comment read on Instagram.

The 2010 book Delay, Deny, Defend: Why insurance companies don’t pay claims and what you can do about it has become a bestseller on Amazon in the week since the murder of UnitedHealthcare CEO Brian Thompson.The book’s title is reminiscent of the three words carved into the bullet casings — “deny,” “defend,” “depose” — found on the Midtown Manhattan street where 50-year-old Thompson was fatally shot on December 4. Luigi Mangione, 26, has been charged with murder in connection to Thompson’s death.