HAMMOND, Ind. —An Indiana man who claimed to run an anarchist group that commanded a couple to kill two Las Vegas police officers had never heard of the pair before the shootings, but his threats to blow up a courthouse and kill judges in the same boastful Facebook posting were taken seriously by authorities, an FBI agent testified Monday.

The testimony helped convince an Indiana magistrate judge to hold Samuel Bradbury without bond on charges of willfully threatening the use of explosive materials and to extort and threaten interstate communication. If convicted on both counts, the 22-year-old from Pine Village could face up to 15 years in prison.

Investigators found no evidence that 765 Anarchists, the group Bradbury claimed to lead, existed or that he had even heard of Jerad and Amanda Miller, who formerly lived in Lafayette, Indiana, before they killed two police officers and another person before dying in a shootout in early June, FBI agent Troy Wohlfert testified.

But when searching the home where Bradbury lived with his parents, police found three bags of aluminum powder and three bags of black iron oxide, Wohlfert said. The substances can be combined to make thermite, an incendiary device.

Bradbury said in the Facebook post that he would destroy the Tippecanoe County courthouse “in a blaze of glory,” and that his group had gathered enough thermite and explosives “to cause extreme damage to the county’s various office equipment, including police cars and buildings.”

Bradbury’s attorney noted that his client also wrote in his Facebook post that his comments were meant as satire.