His later years involved repeated strong statements against transgender and abortion rights which would be highly incompatible with being a Democrat but quite in line with the Trump supporter his neighbors described him as. He also had a history of lying - for example, claiming law enforcement, security, or military experience – and your description of that letter is highly skewed from the mess of conspiracy and likely misdirection people with direct knowledge described it as.

https://www.washingtonpost.com/nation/2025/06/17/vance-boelt...

https://www.startribune.com/vance-boelter-letter-klobuchar-w...