I noticed that too. All those devices. What, did the killer work for the FBI, or something?
Hold that thought.
The "manifesto", if there is such a document, is of no real value. It is a distractor.
What may be really dangerous are the numerous journals and project planning notes compiled by the Nashville crazy. I would bet long odds that those materials identify the people and organizations who recruited her, encouraged her, trained her, and assisted her in her terrorist project.
She had a lot of toys and lots of time to train with them. She did not do this alone. Want to extend that bet? - that some of her backers were FBI informants, or even FBI agents.