I live in Humboldt County (just to the north) and this is a very large problem around here. Growers this violent are rare but definitely out there.

Cops were investigating some cabins that had been broken into and this guy started firing on them with an assault rifle... I'm pretty sure the cops didn't even know he was there, and he had the option to get away. Very dangerous guy. Glad he can't hurt any more people.

I get asked a lot why I arm myself whenever legal while backpacking, as we don't have very dangerous animals in Northern California, and this is why.