SUNNYVALE, CALIF.>> A UPS worker suspected of threatening a mass shooting at the company’s facility in Silicon Valley has been arrested after investigators found numerous firearms and ammunition at his home, police said Monday.

Thomas Andrews, 32, surrendered late Sunday after leading officers on a brief car pursuit on U.S. 101, Sunnyvale police Capt. Dan Pistor said.

Authorities began searching for him a few hours earlier when someone reported that he sent threatening text messages to his employer at the United Parcel Service facility in Sunnyvale,

“He alluded to a mass shooting in his text messages,” Pistor said. “I definitely think we avoided a tragedy.”

When officers on patrol spotted Andrews’ car, they tried to pull him over but he didn’t comply. The suspect kept driving for several miles on U.S. 101 before stopping in San Jose, Pistor said.

“Initially he indicated he wanted to fight with the officers, but then he surrendered without injury,” Pistor said.

Detectives who searched Andrews’ apartment in Sunnyvale found 20,000 rounds of ammunition, five tactical-style rifles, a shotgun, three handguns and body armor. Several backpacks containing ammunition were found by the front door, Pistor said.

Andrews was booked for investigation of making criminal threats, evading police, driving under the influence and several counts of weapons violations. It’s not immediately known whether he has an attorney who could speak for him.

Investigators were trying to determine how Andrews obtained the weapons.

Pistor said Andrews was upset at his employer, but he didn’t know the specifics of his grievances.