(Thanks for the summary bango - I had missed it. Very upsetting.)
In Florida, we have the “Baker Act” (http://en.wikipedia.org/wiki/Florida_Mental_Health_Act) where someone can be involuntarily committed for further evaluation if they are considered a harm to themself or others. Not sure how Cali handles things.
The video is disturbing, no doubt. Police get pretty numb to shit, though. They deal with crackpots (many harmless) all day long. Not hard to imagine what happens when they talk to a clean kid in a BMW who took his meds that day…