If this was a random killer then leaving people behind didn’t carry such a greater risk. Kidnapping 3 people isn’t exactly easy one would assume and carries a even greater risk of losing control at some point. If these women had no idea who was behind this attack then leaving at least 1 behind would make sense. Tons of sexual predators only take one victim due how tough it is to even control one person let alone 3. Logic has to come into play and no forced entry and the fact all 3 women were taken points to somebody who knew at least some of them. Cops have even said the same at some point or another.