NAPA (CBS SF) — A Napa businessman has been arrested for possession of illegal assault rifles, automatic weapons and explosives and was being held on $5 million bail Saturday.

The Napa County Sheriff’s Office said deputies obtained search warrants for the home and business of 44-year-old Ian Benjamin Rogers after receiving a tip that he possessed several illegal guns.

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Investigators found five pipe bombs in a safe inside the suspect’s auto repair shop. The bomb squad created a bunker with used car tires and detonated those pipe bombs.

“It sounded like propane tanks exploding,” said Tyler Rodde, who owns a small business across the street. “We were quite literally blown away by them doing the explosions here on site. That was a big surprise to us. And a total surprise that this was in the neighborhood.”

Napa County Sheriff’s deputies surrounded British Auto Repair on the 1600 block of Action Avenue in Napa on Friday. The department said a tip about illegal weapons led them to Rogers. They raided his business and home and, aside from the pipe bombs, they found about 50 guns.

Deputies said 8 to 10 of those firearms were either illegal or unregistered. They said one was a high-powered machine gun and deputies found 15,000 rounds of ammunition. They also found several pounds of gunpowder they said could be used to make explosives.

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“It comes as a total shock,” Rodde said. “I would expect any amount of ammunition like that to be stored in a more secure facility. I mean he had access to a rocket launcher I believe. That just kind of blows my mind and concerns me a little bit.”

The sheriff’s department said deputies found a weapon that looked similar to a rocket launcher but they needed to test it to be certain.

Rogers’ social media accounts show he’s an enthusiastic Trump supporter. Investigators said they are working with the FBI to find out if Rogers was planning some kind of attack.

The Napa County Sheriff’s Office Twitter account posted about the arrest Saturday night.

Rogers was detained and booked on five felony counts. He was being held on $5 million bail.

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© Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. KPIX 5’s Da Lin contributed to this report