I don’t understand why that means he’s necessarily a white supremacist. For one, chances are he wasn’t all that smart. For two - it could just be that he was an anti-Semite, and so he latched on to Nazi iconography.

yes ok source?

There is a snopes article which goes over the evidence.

https://www.snopes.com/fact-check/allen-texas-mall-mass-shoo...