Another day, another opportunity for domestic terrorists to begin their work on US soil.

Today, the FBI arrested 19 year-old Justin Nojan Sullivan after an extended investigation revealed he may have been plotting ISIS-style attack here in the US.

Officials aren’t yet sure (or haven’t yet revealed) exactly how large of a safety threat Sullivan posed; he was arrested after law enforcement discovered a silencer in the North Carolina home where he lived with his parents. Sullivan had asked a private dealer—in reality an FBI agent working undercover—to build the silencer for him, and bragged to the agent about what he planned to do with it:

…an undercover operative made contact with Sullivan, who allegedly told him, “I liked IS from the beginning, then I started thinking about death and stuff so I became a Muslim.”

The FBI says Sullivan talked about buying an assault rifle from a gun show in North Carolina and shoot people last weekend “because his parents would be out of town at the time.”

He did not buy a rifle before he was arrested Friday but allegedly planned to purchase one at the Hickory Gun Show last weekend.

Sullivan talked a big game, but he wasn’t even on the radar until his father reported his strange behavior to officials earlier this year.

More from the AP:

Federal authorities began investigating Sullivan after his father told emergency dispatchers in April that his son was destroying religious items in their home. “I don’t know if it is ISIS or what, but he is destroying Buddhas and figurines and stuff,” the complaint quotes Sullivan’s father as telling an emergency hotline.

An undercover FBI employee who first made contact with Sullivan in early June said Sullivan described himself as a Muslim convert. Two days later, he said he wanted to kill 500 people but the next day said he wanted to kill 1,000 by using biological weapons, bullets coated with cyanide and a gas bomb.

It appears that Sullivan may have given conflicting statements to his interrogators. He first told the FBI that he didn’t mean to go through with his plans, but then he said he planned the attacks between June 21 and June 23 because his parents would be out of town.

This comes on the heels of several other domestic terror arrests. Last week, 21 year-old Samuel Rahamin Topaz was arrested and charged with attempting to assist ISIS, and with conspiring with three other Americans to join the fight in the Middle East.