TAMPA (WFLA/NBC) – A UPS worker is accused of plotting a mass shooting at the facility he worked at in northern California.

Sunnyvale police arrested 32-year-old Thomas Andrews on charges of criminal threats, evading police, driving under the influence and several counts of weapons violations.

Police say Andrews sent his boss threatening messages indicating he was planning a mass shooting at the UPS facility in Sunnyvale.

When officers tried to stop Andrews’ car he led them on a pursuit.

After officers took Andrews into custody, they searched his home and found five tactical style rifles, a shotgun, three handguns, body armor and 20,000 rounds of ammunition.

Police are trying to determine how Andrews acquired the weapons.