Justin Olsen, an 18-year-old from Ohio, reportedly had 10,000 rounds of ammunition — as well as a vault full of rifles and shotguns — in his family home.
After his arrest, authorities charged Olsen with threatening a federal law enforcement officer.
What are the details?
Olsen, who frequented an online forum, reportedly posted about his ideations of violence on a frequent basis.
According to a report by the Washington Post, Olsen allegedly "praised the Oklahoma City bombing, mass shootings, and attacks on Planned Parenthood."
He also addressed the deadly Waco, Texas, siege, advising people to "shoot every federal agent on sight," authorities said.
"Don't comply with gun laws, stock up on stuff they could ban," he reportedly wrote in another posting. Another posting seemed to reveal a desire to effect political change through violence.
He also reportedly wrote, "Even the Oklahoma City bombing shows that armed resistance is a viable method of political change. There is no legal solution."
Police, according to the Post, "rushed to arrest Olsen just three days after" the mass killings that took place in El Paso, Texas, and Dayton, Ohio. The attacks, according to the Cleveland Plain Dealer, were a justification to expedite the investigation and subsequent arrest.
Authorities charged Olsen on Monday with one count of threatening to assault a federal law enforcement officer.
During interviews with officials, however, Olsen insisted that he is not violent and said that the posts in the online forum were "hyperbolic" in nature and "only a joke."
Referring to his suggestion to shoot federal agents, Olsen explained, "That's a hyperbolic conclusion based on the results of the Waco siege." He also noted that "ATF slaughtered families" during the incident.
Olsen is due back in court on Friday.