A California UPS worker who police say threatened a mass shooting was arrested Sunday following a vehicle pursuit, and police found a cache of firearms and ammunition inside his home. They also found backpacks full of loaded magazines and a ballistic vest.

Thomas Andrews, 32, sent threatening messages to his employer, the Sunnyvale Department of Public Safety said in a statement posted on Facebook. The text messages said Andrews was planning a mass shooting at the UPS in Sunnyvale, the department said. 

“He alluded to a mass shooting in his text messages,” Sunnyvale police Capt. Dan Pistor told the Associated Press. “I definitely think we avoided a tragedy.”

Police launched an investigation and learned Andrews was the registered owner of four handguns and a rifle, Sunnyvale DPS said. Patrol officers found Andrews and attempted to pull him over late Sunday, but he led officers on a car chase, USA Today reports.

He was eventually captured on Highway 101 with help from the California Highway Patrol, according to the department. 

Sunnyvale detectives executed a search warrant on Andrews' home, where they found: "over 20,000 rounds of handgun and rifle ammunition, numerous high-capacity magazines, 5 tactical style rifles, 1 shotgun, 3 handguns, and body armor. Several tactical backpacks containing ammunition were staged at the front door of the apartment where the suspect resides," Sunnyvale DPS posted on Facebook.

Andrews was arrested and booked into the Santa Clara County Jail on charges of making criminal threats, evading police, driving under the influence and "several counts of weapons violations," according to Sunnyvale DPS.