The patch highlighted used by the shooter is the (supposed but not actual) flag of Blackbeard, the FOG patch is a modified version it. I see the Blackbeard patch and flag fairly often in the US from not necessarily white-supremacist but right-wingers or pirate fans in general.
https://en.wikipedia.org/wiki/Flag_of_Blackbeard
The patch highlighted used by the shooter is the (supposed but not actual) flag of Blackbeard, the FOG patch is a modified version it. I see the Blackbeard patch and flag fairly often in the US from not necessarily white-supremacist but right-wingers or pirate fans in general. https://en.wikipedia.org/wiki/Flag_of_Blackbeard