I haven't seen anything yet. Seems like he had a very minimal online presence, and was about as close to a Lone Wolf as you can get. There doesn't appear to be any indication that he was 'leaking' prior to the assaination attempt either.
Giving off information that he was planning some kind of mass murder or assassination attempt. Many people that plan that kind of thing 'leak' information about it before hand, through things like Facebook posts, or remarks to people they know, etc. Very few people are good at keeping that kind of thing truly secret.
The first rule of Successful Secret Assassin Club is zero your rifle, but the second rule is don't talk about Successful Secret Assassin Club.
Supposedly he was using Signal or the like encrypted messaging app, " to talk to someone overseas". Nothing more. I don't know what if any sources exist for that or what it matters. Please correct me if you have sources.
Sometimes I just turn on the crazy right wing news channel, and also i listen to Knowledge Fight, but the crazy might be leaking into my brain.
Given the fact that neither side demonized him, this may be one of the few cases of actual "mentally unstable lone wolf" with no sane or reasonable motive.