California issues very few concealed handgun permits and Ventura County is below the state per capita average rate, but permitted concealed handguns are banned in any place that serves alcohol for consumption. Below is a picture of the first page of the concealed handgun permit application for California.
It appears unlikely that the security guard at the bar was armed, but people who are recognized as security guards have an incredibly difficult job stopping these attacks. The same is true for the sheriff sergeant who entered the bar to stop the attack.
Recent cases where concealed handgun permit holder have stopped mass public shootings are available here.