When we look at the wording on the Richard Nixon Postcard "Dear King, We know where Patty Hearst is. But wait till we get your daughter. A concerned citizen for freedom", the comparisons can be noted. With the Citizen Card sandwiched in between the Dear Mr. Chancellor Letter and the "Dear King" Richard Nixon Postcard, we have more cause for concern about the validity of the May 8th 1974 communication as a Zodiac Killer offering. It was directing its consternation at the running of ads by the San Francisco Chronicle and Examiner - two newspapers previously highlighted with ire by the Symbionese Liberation Army because of their connection to Randolph Hearst.
To view the entire FBI documents on this matter, visit page 400 of the Hearnap files, part 36 of 42.