“You will have to kill me and my family before you get my guns," it continued, adding anyone attempting to seize her firearms would "get shot in the face."
Richardson was arrested earlier this month. She worked as an actress and had minor roles on shows including the Walking Dead and the Vampire Diaries.
The Justice Department said Friday that the case was under investigation by the FBI, U.S. Postal Inspection Service and Secret Service, as well as local authorities.
The charges are separate from another set of three ricin-laced letters sent earlier this year. Mississippi resident James Everett Dutschke was charged in that incident and is accused of sending letters laced with the poison to Obama, a Mississippi judge, and Sen. Roger WickerRoger WickerAs US healthcare changes, preventative screenings can't stop A guide to the committees: Senate Pruitt confirmation sets stage for Trump EPA assault MORE (R-Miss.).
— Updated at 1:20 p.m.