If the twins were not shot first, they slept through a lot.
It was such a big house, with 3 stair cases, thick doors and walls. He would have been confident they would not wake. He was right.
The rifle would sound quite loud being fired indoors, I would have thought the last thing Bamber would want is to shoot two young children while they were running around screaming, if they ran and hid they would be hard to find in such a big house.
If the shooter is Sheila I would have thought the children would naturally be first but Cc must have spotted something that I have missed?
My best guess is the Children were already shot when Nevil comes across Sheila in the kitchen, I think the shots were fired all in one go Sheila only being able to load 8 bullets into the magazine.
Perhaps Cc or someone can show me why the twins were not shot first?