Neither Nevill or Sheila would have received any injuries. Nevill would quickly negate the situation. Either when getting close enough to her, or using an object to charge her. Sheila would offer no resistance if trying to hold onto the rifle.
As head of the family Nevill had no choice but to quickly negate the situation & there is zero chance he would want to leave a message on his sons answering machine at 3am.
He was twice as big strong, fit and alert as Sheila & would not be pleased at being kept awake. The rifle was used for shooting rabbits.
Nevill would have to decide whether to tell June & anyone else the following day. Although it is likely June would have also been awake and out of bed.