Here is one suggestion...
Four years ago, the CT announced that a letter several pages long, had come to light addressed to 'Mummy', which was claimed as referring to Sheila's natural mother Christine (and claimed that Sheila described June Bamber as 'Mother').
They claimed there were a 'number of angry references to her ex-husband the twin’s father, Colin Caffell who wanted full custody of the children'.
Apparently within the letter, Sheila indicated that she would be 'in the other world,' after the police arrive, and wrote 'my babys and me we go to our rest.'
Furthermore, she made reference to 'us' being put into a deep trench after the police arrive.
The CT claimed to have received a 'preliminary overview of the material' 'provided to a handwriting expert - who believes that the material was written by Sheila Caffell'.
Apparently the letter was revealed in 2011. I am unsure why it was not acted upon sooner. However, I'm aware that the CT were made up of volunteers and were/are dependent upon funding for expert assessments / forensic analysis etc.
As most people know, Jeremy Bamber claimed there was a conversation around the dinner table regarding 'fostering' about which, people have argued either wouldn't have been mentioned at all - or - may have been mentioned in the context extra help for Sheila. Perhaps Nevill and June were worried that they might lose contact with the twins, if the situation continued without some type of intervention or influence brought to bear? Perhaps they sensed that in the future Colin might act decisively, to shield the twins from June's religious bent?
We know that instead of portraying Sheila as having been enraged or merely annoyed or sulky, Bamber portrays her as having seemed vacant. If his portrayal is accurate, what may have been behind her vacant stare? What might Sheila have ruminated on, as late evening crossed over in to the small hours?
Could it be that Sheila had lost all hope that she could keep her babies with her in this world? Did she reason that if she could not keep her babies with her in this world, her only choice was to keep them with her in the next?
When Sheila had 'gone berserk' with one of Nevill's guns, could it be that in her own mind, she was simply enacting the safeguarding of her self and her babies as a unit, together, in the next world?
Is it possible that either Nevill or June or Nevill and June were killed by Sheila because they interfered with Sheila's mission to send herself and her babies to their rest?
If Sheila has shot the twins and thinks they may be dead - she has to then ensure that she herself is killed, in order to be with them on the other side. Otherwise, she will have sent her babies over to the other side without the protection of their mother. If Sheila was prevented from joining her babies by the intervention of one or both parents, might she not have experienced anguish, panic and an incredible sense of urgency to complete her mission?
If Sheila has shot the twins but is unsure as to whether they are dead, the situation is no better for her - because there is now no going back. Again, in this scenario, Sheila must complete her mission.
We cannot know to what extent Sheila may have experienced auditory or visual hallucinations but we can try to imagine her as experiencing thoughts that we would view as warped but which she may have viewed as being cogent and meaningful. Perhaps even forceful to the point of being demonic in their insistence (that she carry out her duty).
I don't think Nevill or June stood much of a chance. They didn't know what they were up against. It was the small hours and the situation was one of pure dread. Nevill is presented with a situation of having to either kill or save his own daughter - who may be locked up for years in an institution. He cant save her without possibly losing his own life. Can he bring himself to kill her? Can he overpower her with his wounds? What will happen to his wife if he fails? The anguish and dread they must have felt regarding the fate of the twins is horrific.