The article's author was suspicious and skeptical too. That's why he read through the chat logs and audio recordings, and also interviewed former friends and militia members to corroborate the story. The article also explicitly calls out which of Williams' claims were uncorroborated or contradicted.

Genuinely asking: what other evidence are you looking for?

Logging my doubt that the target of your comment actually read the entirety of the article.

I think he actually agreed with it. Then had a change of heart or they pissed him off. I would go with the latter. Myself. Plus really have to be careful doing solo stuff like this. Alot of actual bad guys would say. See I was telling a journalist etc. I am super under cover!