I was watching a program about the Zodiac killer; in it, the interviewed a San Francisco cop who was on the street back then.
He said “in 67, the kids were told to bring flowers if they came to San Francisco. By 68, it would have been a good idea to bring a revolver.”
I lived in the area back the. Was afraid to go out at night because of the Zodiac Killer.
I don't know about that but I have heard that one thing that led to the decline of the hippie scene in SF was that the news about them drew in a rougher crowd more connected with biker gangs and amphetamines instead of pot and LSD.
In 1967 there was a "hippie funeral" parade in SF that was supposed to symbolically mark the end of the movement. There were Hells Angels in the parade. This was at a time when many people in the rest of the country were still first hearing about hippies.