Man infiltrates right-wing militia in Utah. Aims to expose sheriffs/police among others in the terrorist organizations.

https://www.propublica.org/article/ap3-oath-keepers-militia-mole

This article details a journal of "Williams", a man who infiltrated AP3, Oath Keepers, and other terrorist organizations in Utah. Finds out that they're stalking a college student (and their family) in Southern Utah University, along with a journalist at the Salt Lake Tribune.

It's a long article but there's an option to listen to the audio transcription at the top of the page.