I think the murders of the kids were much more violent. He makes it sound like he sent them to la la land, covering them kindly first with a soft blanket. Violent meaning pushing their heads harshly, as they would instinctively shake their heads and bodies to get air. I'm not disbelieving that he killed them at the crude oil tanks, just that I think they were probably killed nearly at once, and he made one trip up the tank stairs. Sites are quoting that he said he killed Cece, walked way over to the tanks (he was parked over by the well head, across the parking lot) and Bella sat there placidly waiting for him to get back. I don't recall his saying that he took Cece up to the tank before he killed Bella. I think he said "Cece was first". The sun was up then, it wasn't dark and scary outside. Anyway I think he said Bella undid her seatbelt, when in her life would she have been exposed to that sort of seat belt? In the car seats? So I think they were killed instantly when he got there, and taken to the tanks. I don't believe he would have dragged out poor dead SW in front of the kids, while their feet were probably right on her.