It is likely that the dog would bark when the shooting started at least - risking to wake up Sheila. I have been bashed plenty for that statement, but I do stand by it. Can´t see it is far fetched at all.
Barking, shouting, screaming, gunshots, moving downstairs, one in agony, the other in a frenzy - who´d sleep through that?
I don´t think people tiptoed around whispering that night.