I'm inclined to go with the possibility that the killer was known to those street-women, as you suggest.
He was known to the area, he frequented it regularly, but he didn't have to live there.
Others have commented on his ability to avoid detection, that he knows the backstreets well, that he is able to blend in as he obviously must have been seen by someone, but he did not attract suspicion.
In my opinion, he was a familiar face, the women knew him, and as is often the case, was likely questioned by police at some point.
Regards, Jon S.