From what I understand, it is very difficult for a member of the general public in my state (California) or at least my county and surrounding ones to get a concealed weapons permit unless you can prove that you're truly in danger and really need to carry a gun.
For example, here's what a police dept in my county says about CCW:
San Jose Police Department.
Santa Clara County sheriff draws legal fire for way she hands out concealed-gun permits – The Mercury News is a story on my county from 2011. I found
Requests to Carry Hidden Guns Skyrocket in Santa Clara County from 2015 w/some (tiny) numbers. (Santa Clara County has a population of over 1.9 million. City of San Jose is just over a million of that.)
Tesla's Fremont plant is in Alameda County, which is right next to mine. The man in question resides in Oakland, which also is in that county. Search
Concealed gun ruling stands: Foes can’t fight loosening of California permit standards – East Bay Times for Alameda.
From some digging (not sure how accurate the sources are) of supposed numbers of valid CCWs in various CA counties, it's unlikely the employee had a valid CCW.