GREENWOOD, Ind. (AP) — Authorities say they believe an Indianapolis man was planning an act of domestic terrorism after a search of his car revealed a rifle, ammunition and liquids that when mixed form a toxic and combustible gas.

Thirty-one-year-old Christopher C. Byrne was pulled over by a Greenwood police officer on Aug. 15. Police say Byrne said he was a “sovereign national” and refused to provide identification. Police identified Byrne, determined that he’d recently pleaded guilty to a gun charge and a felony charge of being a habitual traffic offender, and arrested him.

Johnson County Deputy Prosecutor Rob Seet says the water bottles containing ammonia and bleach suggests Byrne might have been planning “something bad” and that the case is being investigated by the federal Bureau of Alcohol, Tobacco and Firearms.