How did he do it?

[adam]

It was not hard to commit the massacre.

At 2am, it is the perfect time for an execution. Everyone was asleep. Neville waking up seconds beforehand. But everyone else shot while asleep. Sheila then either lead of carried to the main bedroom. Although there is a slim chance of her waking and retreating to the far corner of the main bedroom.

Colin Caffell said Sheila would have shot herself with the twins.