They reported users/posts for review. Happens on my forum all the time from all sorts of users (public, lawyers, etc). Up to the publisher to make their call from that point. In one case I bothered reading in this set, they mentioned that legal docs would follow if they were seeking to identify and pursue an author (pre-action discovery).
It didn’t seem that the FBI were going into detail on any cases. I wondered if some were likely to be considered concerted foreign interference that they’d unearthed and policing that was within their remit. I assume there’s some overlap between Twitter’s ToS re misinformation and the FBI’s assessment, if that makes sense.