In an online forum, he went by the name “ArmyOfChrist,” and praised the Oklahoma City bombing, mass shootings and attacks on Planned Parenthood, the FBI says. When the deadly siege in Waco, Tex., came up, he allegedly offered one lesson: “Shoot every federal agent on sight.”

“Don’t comply with gun laws, stock up on stuff they could ban,” he allegedly wrote in another post. “In fact, go out of your way to break these laws.”

The comments were all written by an Ohio teenager named Justin Olsen, the FBI says in federal court documents. And when agents raided a home where the 18-year-old lived earlier this month, they found about 10,000 rounds of ammunition and a vault full of assault-type weapons and shotguns.

On Monday, Olsen was charged on one count of threatening to assault a federal law enforcement officer. His case comes as federal agencies face mounting pressure to root out homegrown terrorists in the wake of two mass shootings earlier this month and amid a national upswing in violent right-wing extremism.

Police rushed to arrest Olsen just three days after mass shootings in Dayton, Ohio and El Paso, with a local prosecutor citing the attacks as a justification for an urgent arrest, the Cleveland Plain Dealer reported.

In interviews with federal authorities, though, Olsen insisted that he was no violent extremist. Asked about the postings, the teen said they were “hyperbolic” and “only a joke.” His attorney didn’t immediately return a message from The Washington Post.

Olsen’s posts, which came on a meme-heavy website and app called iFunny, first caught the eye of an FBI agent in Anchorage, who noted a surge of new subscribers to the “ArmyOfChrist” account. The account’s posts included regular far-right, white-nationalist memes, reported BuzzFeed.