PHOENIX (AP) — A firearms dealer in Arizona sold weapons to an undercover federal agent he believed would help him carry out his plan for a mass shooting targeting minorities, an attack that he hoped would “incite a race war,” according to a federal grand jury indictment.

Mark Adams Prieto was indicted Tuesday by the grand jury in Arizona on charges of firearms trafficking, transferring a firearm for use in a hate crime, and possession of an unregistered firearm.

Court records didn’t list an attorney who could comment on Prieto’s behalf. A lawyer who briefly represented Prieto after he was arrested last month in neighboring New Mexico didn’t respond Wednesday to a request for comment.

The indictment says the 58-year-old from Prescott, Arizona, recruited the undercover FBI agent and an informant at a gun show where Prieto was a vendor.

According to the indictment, Prieto told them he’d been thinking about carrying out a mass killing of minority groups for some time in order “to incite a race war” ahead of the presidential election in November. Prieto later identified a rap concert in Atlanta in mid-May for the attack, the indictment alleges.

RELATED COVERAGE Lauren Boebert’s ex-husband pleads guilty to reckless endangerment after altercations with family Union: 4 Florida police officers indicted for 2019 shootout that left UPS driver and passerby dead Judge strikes paragraph from Trump classified docs indictment but denies request to dismiss charges

The indictment says planning for the shooting began in January and took place over several months at gun shows around Arizona, including in Phoenix and Tucson. At the gun shows, the indictment alleges, Prieto sold two rifles to be used in the shooting to the FBI agent.

Prieto was arrested in New Mexico on May 14 — around the time of the Atlanta concert — while driving east from Arizona. Authorities said they found seven firearms inside his vehicle.

Following his arrest, court records show, a U.S. district judge in New Mexico ordered Prieto to remain in federal custody, saying the “seriousness of danger to the community is extreme” if he was to be released.