Samson told authorities he heard voices in his head and had visions, including one of the church he's accused of targeting last month.
“I figured that there was something there,” “alt-right” activist Brad Griffin says.
Two people were wounded in what police said was a disagreement over a dice game.
The case is seen as highlighting growing concern about Internet-based directives from Islamic State leaders.
Family members identified the victim as Navy Petty Officer 2nd Class Randall Smith.