The FBI arrested an 18-year-old from Ohio for making online threats — including against the federal government and Planned Parenthood — and found a large cache of weapons, authorities said.

When agents raided the Boardman, Ohio, house where Justin Olsen was living they recovered 15 rifles, 10 semi-automatic pistols and roughly 10,000 rounds of ammunition, according to a criminal complaint written by FBI Special Agent Themistocles Tsarnas and seen by NBC News.

Olsen, who wrote under the name "ArmyOfChrist," was charged Monday with one count of threatening to assault a federal law enforcement officer.

"ArmyOfChrist discussed supporting mass shootings, and assault and/or targeting of Planned Parenthood," according to Tsarnas.

Read more: NBC News