You know, thinking about it, we dont know that the killer(s) was in a truck, or a car, or a 4wheeler, or just walked up on them. All we know is that someone saw the poi in a pickup in the area, around the same time. I've been out there. Lots of people take that road. That is why I believe the timeline is tight, or someone would have seen the girls, besides just one witness who isnt saying anything public. It wasnt even said that he saw the poi... just the girls, shortly before they were killed. So did he see the poi? or was someone just passing through, before the girls left the house, and they saw the poi stopped on the road, (possibly to relieve himself, check something that may have fallen in the floorboard of the truck, like a cigarette lighter or something, checking his tires, whatever he was doing or just finished doing when he was seen by the witnesses) and maybe he just went on.
This is what the osbi says when they say they believe he may have seen something, so they want to question him. They never have said they believe he did it. But they have never said they think he didn't either. So we dont know what the killer(s) was/were driving... if they (he/she) were even driving anything.
Just something to keep in mind. We just have no details.