Funny stat. Majority of murders happen in family. The recent FBI stat says that family members were responsible for 43% of them. Gangs are responsible for about 30%.
Now since large number of families moved out from SF, and there are more no big local gangs (since there are no families) you have about 40% more random homicides. And these random ones are the worse and the most scary ones.
When crime stats say "gangs" they're not just talking about a street gang with a name, list of members, defined territory and stuff like that.
They're also talking about people who engage in business that is not state sanctioned and therefore have to settle disputes with their own violence instead of getting a court to threaten state violence on their behalf. One part time drug dealer rounding up a couple buddies and putting a bullet in a guy who ripped him off will show up as and makes up a huge chunk of what's considered "gang violence" in these stats.
When comparing cities it's useful to differentiate between random crime and crime where the parties to know each other.
The scary part of SF homicides now that you can be walking around and some crazy guy just shoots you or stab you without any reason whatsoever. They are not professional criminals: they are just so drugged up or whatever.
I think that should be rephrased, I see what you mean but it sounds weird to call 43% a majority since the other 57% of murders are not family related.
Now since large number of families moved out from SF, and there are more no big local gangs (since there are no families) you have about 40% more random homicides. And these random ones are the worse and the most scary ones.