In San Francisco at least, it really does mean nothing happens. There have been instances of stabbings (non-lethal) and the perpetrator was spotted in public days later.
The vast majority of those incidents involve the homeless, though, even though they're not all reported that way. There's a ton of issues to unpack there so I won't even bother trying, but nonetheless it's a distinction that matters at least in terms of understanding what's happening and why.
