I would at least have either tried to hide somewhere in the farmhouse as it was big enough,or else made my way somehow,to the front door,if I'd been either June or Neville,or even lifted a window up to shout out of it even though I probably wouldn't have been heard,but at least it would have shown that the tragedy wouldn't just have been contained in just one or two areas.
It appears that no attempt was made to protect the children,by the mother ? If Sheila had thrown herself upon the children,which any mother would have done,then Sheila would have had shots in her back,the risk anyone,including myself, would have taken to have saved the boys.
No attempt was made to open the front door,as it remained locked.
Sheila herself would have been free just to dial 999 as police would have picked up the address via the operator.
Nobody can be in two places at once,both upstairs,then downstairs-----------3 flights,so ample time to dial for help from any one of them.
I'm more than convinced that had it been Jeremy as the murderer,he'd have been shot somewhere,as there was a shotgun to hand and all it needed was to have aimed at his legs to brand him the murderer.