The FBI says it found 10,000 rounds of ammunition, 15 rifles and shotguns, and 10 semiautomatic pistols at the home where Justin Olsen was living, according to court documents.
The 18-year-old was charged Monday with one count of threatening to assault a federal law enforcement officer.
He initially appeared in court for a bail hearing on August 8, following his August 7 arrest.
He came to the attention of federal investigators looking into posts and memes on a website and app called iFunny.
On that site, he allegedly posted that the lesson offered by the 1993 Waco, Texas, seige was to, "Shoot every federal agent in sight." In other posts, he wrote, "Don't comply with gun laws, stock up on stuff they could ban," and "In fact, go out of your way to break these laws." Olsen was arrested just three days after the mass shootings in Dayton, Ohio and El Paso, Texas.
In July, FBI director Christopher Wray told the Senate Judiciary committee, "a majority of the domestic terrorism cases that we've investigated are motivated by some version of what you might call white supremacist violence, but it does include other things as well," Justin Olsen has another court date Friday.