shiiet, they might think people on discord helped him wtf
I think he used a lot of chat programs. Don't forget Steam, the websites were he was active and possible the Xbox Chat. I've only talked with Sephiroth about Return to Blockland and the development of Blockland Classic Mod. So I'm not worried and I can understand that they are looking for clues. Spoken about Steam.. someone admitted on Sephi's steam profile that he had contact with another/other shooter(s).
But I haven't really spoken to Sephiroth since September as I were busy with work and other stuff. So mostly I haven't even read the messages he sent me on Steam.
As far I know is that nobody on the Discord forced him to do this. They even had no clue that he was planning the attack.