From an interview with a local politician who had gone door to door canvassing and had just talked to the guy weeks earlier, it turns out he was a particularly psychotic anti-mormon zealot.
It was just pure hatred for mormonism (?)
https://www.freep.com/story/news/local/michigan/2025/09/29/thomas-jacob-sanford-michigan-shooting-suspect-anti-lds-tirade/86415139007/Quote
But Johns said everything Sanford asked him about Mormonism led to Sanford declaring the religion as "the antichrist."
Their conversation never delved into politics or current events, Johns said — "there was no mention of anything right or left, blue or red.”
I don't really have anti-mormonism on my bingo card so I'm not sure its a round peg you can fit into square holes of ideologies.
Dude just had some very serious animus towards the LDS church for some unclear reason