They have the video linked right on the first post here: https://kiwifarms.net/threads/mass-shooting-streamed-on-twitch-payton-gendron-jimboboiii.119000/#post-11895832 The 7 minute one is all that's available: actually maybe I shouldn't post that publicly on this site, it's under a spoiler tag you have to click there.

It's hard to search for these things because most the goddamn search engines won't show you relevant results with regard to sensitive content like this. I just knew if it was going to be posted anywhere, those dudes would find a way.