If the silencer made the rifle silent/near-silent, then why does Jeremy only shoot the twins twice in the first firing round? If firing multiple times into the poor twins was part of Jeremy's staging to make it look like Sheila did it, then why not fire more there and then before going downstairs to reload? After all, the rifle is silent, you say, so what would he have to worry about?
Also, since the rifle is silent, and given Jeremy's precision shots into the twins, how does Nevill end up outside the master bedroom and fleeing for the kitchen? Adults are larger targets than children and both Nevill and June were in bed, having not been disturbed by the silent killer prowling around the house. Whichever way you look at it, they're sitting ducks. What's the problem?