Ziz (the cult leader) had a blog at sinceriously.fyi, where she elaborated on her philosophy. The blog has since devolved into a string of death threads and subsequently been deleted, but anyone who's interested in the backstory can still find some posts on archive.ph (e.g. [1]) and more on web.archive.org.
From Ziz and other cult members' writings, it's obvious that the cult has been in conflict with the rationalist community, rather than part of it, for years. It's disappointing but not surprising that SFGATE decided to pin the murders on the rationalist community while contorting their writing to avoid mentioning the elephant in the room: the cult leader is a trans vegan, almost all of the members are also trans vegans, and these are core parts of their ideology. They were discussed over and over on Ziz's blog.
In fact, after the katana stabbing and the self-defense shooting by the wounded landlord, another cult member used her blog to blame Zack for the events. Zack wasn't involved, physically present, or in communication with the cult at the time, but he does believe in a different theory of transness than they do [2], so they can't stop being enraged at him. That theory was actually one of the main reasons the cult has split off from the rationalist community. I'm worried that Zack may be in danger.
[1] https://archive.ph/jChxP
[2] http://unremediatedgender.space/about/