FBI counterterrorism agents have arrested and charged a Detroit man on accusations that he illegally purchased an arsenal of weapons and discussed carrying out an attack.
Sebastian Gregerson, 29, who also goes by Abdurrahman Bin Mikaayl, was arrested Sunday after he met an undercover agent at a gas station and traded a handgun for grenades, according to a criminal complaint.
Authorities charged Gregerson on Monday with unregistered possession of a destructive device and unlicensed receipt of explosive materials. He faces up to ten years in federal prison if convicted.
Gregerson came under FBI surveillance in April 2015, when the agency was alerted that he possessed grenades and bazookas capable of mass casualties, according to court records.
Since beginning the investigation 16 months ago, the FBI said Gregerson has bought a cache of weapons, hundreds of AK-47 ammunition rounds, tactical gear, and commercial-grade road spike intended to slow or disable vehicles.
"In my training and experience, and that of other agents upon whose expertise I am also relying, the purchase of training versions of these weapons makes it unlikely that the weapons were purchased for recreational use, such as hunting," an FBI special agent wrote in the complaint, the Detroit News reported Monday.
The Detroit News also reported that a Facebook account belonging to a user of the same name from Dearborn, Michigan, just outside Detroit, contains an image of a man riding a horse and carrying an Islamic State flag.
ISIS supporters have used this image in the past, according to Seamus Hughes, deputy director of George Washington University’s Program on Extremism, who said "that suggests to me that he is a supporter [of ISIS]."
Gregerson discussed ways to attack buildings and law enforcement with homemade grenades in a recorded phone conversation with an undercover FBI agent.
He is due back in federal court Thursday at the Theodore Levin U.S. Courthouse in Detroit. He is currently being held temporarily without bond.