US Dept. of Justice said:
The criminal complaint was filed today in federal court, charging Justin Nojan Sullivan, 19, of Morganton, North Carolina, with [...], one count of transporting and receiving a silencer in interstate commerce with intent to commit a felony, and one count of receipt and possession of an unregistered silencer, unidentified by a serial number. Sullivan was arrested in his home on Friday, June 19, 2015, without incident.
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According to the criminal complaint, an FBI undercover employee (UC) made contact with Sullivan beginning on or about June 6, 2015
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According to the complaint, on or about June 9, 2015, Sullivan discussed with the UC the possibility of making homemade silencers and asked the UC whether he would be able to make one. When the UC said that he thought he could, Sullivan told the UC “Ill need to have one built by next week.” The complaint alleges that Sullivan also told the UC “Yeah ill let u mail me…I plan on using it this mont[h].