Interesting Cc what have I missed that tells us this?
Julie said the twins were shot first.
It was such a big house with 3 stair cases, thick doors & walls. He would be confident enough to shoot them first. Once each.
He can test the rifle on them. Silently with the silencer.
It is a good way to get started. Killing two people with 2 bullets & having 9 bullets left.
Once he has shot the twins, there is no going back & he is pumped up. He will not hesitate in the main bedroom.