A man was arrested Saturday outside former President Trump’s rally in Riverside County on suspicion of illegal possession of a shotgun, handgun and high-capacity magazine, sheriff’s officials said.

Vem Miller, 49, of Las Vegas was booked at the John J. Benoit Detention Center in Indio on charges of possessing loaded firearms, Riverside County sheriff’s officials said. He has since been released on bail pending a court appearance.

Deputies found the guns after searching Miller’s black SUV at a checkpoint at Avenue 52 and Celebration Drive in Coachella about 5 p.m. Saturday, authorities said.

At a news conference Sunday, Riverside County Sheriff Chad Bianco said his deputies had likely thwarted an assassination attempt, although he acknowledged “there is absolutely no way any of us are going to truly know what’s in [the suspect’s] head.”

According to Bianco, Miller had driven his SUV through an outer perimeter maintained by sheriff’s deputies before he was questioned at a checkpoint closer to the rally entrance. Miller claimed to have credentials to attend the rally both as a journalist and VIP guest, but couldn’t produce any documents.

The deputy questioning Miller noticed what Bianco called “many irregularities” with his SUV: The license plate was phony, the vehicle was unregistered and the interior was “in disarray,” the sheriff said.

A search of the SUV turned up fake passports and driver’s licenses with different names, guns and ammunition, Bianco said.

Bianco said he was identifying the suspect as Miller “with an asterisk” because he possessed identification with multiple names. The suspect stated his name was Vem Miller, according to the sheriff.

The homemade license plate was “indicative of individuals claiming to be sovereign citizens,” Bianco said, referring to an ideology whose followers do not consider government authorities to be legitimate. Bianco called it irrelevant that most sovereign citizens subscribe to far-right beliefs.

“He was a lunatic,” the sheriff said.

Asked whether he was speculating by branding Miller a would-be assassin, Bianco said it was “common sense” to suspect that someone carrying guns and fake identification to a political rally intended to hurt people.

“We know that we prevented something bad from happening,” said the sheriff, who attended Trump’s rally himself. “It’s irrelevant what that bad was going to be.”

Bianco said the investigation into Miller’s intentions would be handled by the U.S. Secret Service and Federal Bureau of Investigation. In a statement Sunday afternoon, the U.S. Attorney’s office in Los Angeles said prosecutors and agents of the Secret Service and FBI were investigating.

Trump narrowly avoided an assassination attempt in July at a rally in Butler, Pa. A bullet grazed his ear before snipers assigned to his Secret Service detail killed the gunman, Thomas Crooks, who had opened fire from the roof of a nearby building. A rally attendee, Corey Comperatore, was killed shielding his family from the gunfire.

In September, police arrested a man near Trump’s golf club in West Palm Beach, Fla. They suspect that Ryan Routh intended to shoot the former president with an SKS rifle while hiding in the shrubbery lining the golf club.

Prosecutors say Routh possessed a handwritten list of dates and venues where Trump was expected to appear.

Routh is charged with attempting to assassinate a presidential candidate, possessing a firearm in furtherance of a crime of violence, assaulting a federal officer, possessing a firearm and ammunition as a felon and possessing a firearm with an obliterated serial number.