In the vicinity of any city or town there is usually no shortage of violent criminals... as in the late seventies these criminals could get away with their crimes more easily, when DNA was not what it is now and there were no surveillance cameras in On all the streets, people tend to link unsolved cases to the few "known" repeat offenders in the area, even though there is no evidence to support it... I'm sure she was kidnapped by a psychopath, but I wouldn't say it's necessarily a serial killer in the sense that he had a series of murders behind him... although perhaps he is a serial killer who was never arrested...
I also see that San Pablo is not such a big city (today it has about 30,000 inhabitants, probably less in 1979). People tend to know each other in those communities (which is why I believe in the sightings at the mall after she left the store)...rather than an out-of-town serial killer who lived somewhere in the area, I'm leaning more to think about a local weirdo hiding in plain sight, who might have previously met the victim (even superficially) and convinced her to come with him or help him store something in the back of his truck. I think this scenario is more likely here than a stranger who appears out of nowhere and covers your mouth with a towel soaked in ether...there are no witnesses, no clues, no clues, no evidence of a crime, just one. girl who disappeared into thin air...
either way
rest in peace
