The Springfield Three: Was the perpetrator(s) known to the victims, or was it a stranger?

The Springfield Three: Was the perpetrator(s) known to the victims, or was it a stranger?

How can 3 grown women just disappear without a trace without leaving any signs of a struggle or without causing any commotion whatsoever? I would imagine that it would be extremely risky for a stranger to attack a house with 3 random vehicles in the driveway, without knowing who was inside. on the other hand, if the perp(s) did have some close associations with the women, i feel like they would have been identified by now. For those of you who are unfamiliar with the case: https://en.wikipedia.org/wiki/Springfield_Three

This is my number 1 pet case. all of this makes me think that whoever did this knew that there were only women who lived in the house. this is such a frustrating case and i simply cannot picture what or how this happened. for all they know, it could have been some big grown man with a gun.