The casings had the words "deny", "defend", and "depose".
So unless this is a false lead meant to distract people from the identity of the actual killer, it is likely related to a decision made about a United Healthcare policyholder.
"deny" = deny authorization for some kind of expensive medical care
"defend" = defend the decision
"depose" = when sued about the matter, start deposing as many people as possible in order to make the decision look correct