The explanation states Neville was already up and awake, although still bare footed and in pyjamas when Sheila opened fire on the twins.
Neville had obviously not attempted to get the rifle off Sheila beforehand, and then allowed her to go into the twins bedroom and open fire. June was awake but apparently too afraid to assist Neville or the twins.
Neville watches Sheila open fire into the heads of the twins. However still decides to not attempt to restrain Sheila. Instead allowing the twins to die while he goes downstairs and spends several minutes ringing a 'sleeping like a log' Bamber'. Then the police 16 minutes later.
No request is made by Neville for medical assistance to Bamber or the police.
Sheila for some reason had only fired 8 of the 11 bullets into the twins, before deciding to reload. Neville does not notice Sheila reloading. Or does notice and does nothing, preferring to wait for Bamber and then the police 16 minutes later to answer the phone.
Sheila firing 8 bullets into the twins and then reloading takes well over 16 minutes, as Neville has by now rang and said 11 words to Bamber, and rang and spoken to the police 16 minutes later.
June has still not left the bed, although the twins have been shot and Sheila has been downstairs reloading for over 16 minutes.
June is laying down with her head on the pillow as Sheila goes back upstairs and fires into June's head and body. There is no evidence of any resistance from June.
Neville has let Sheila re load and go back upstairs with a fully loaded rifle. Or had not noticed Sheila doing this over the last 16 minutes.
Neville has excellent ears and when hearing upstairs gun shots finally decides to confront Sheila. It is a tradedy and massive error that Neville did not confront Sheila pre shooting.
Neville rushes upstairs unprotected, barefooted and in pyjamas.
Upon arriving upstairs Sheila accurately fires four bullets into a moving target. Two shots hitting Neville's head.
Despite rushing upstairs to confront Sheila and Neville's upstairs shots being from close range, he still does not physically confront Sheila, but instead runs straight back downstairs.
Although there is a mass of evidence of a brutal kitchen fight - bruises, abrasions, black eyes, broken nose, broken rifle stock, bloodied rifle, broken watch, smashed and upturned furniture, Neville apparently just collapses when arriving in the kitchen and there is no fight.
After firing several final shots into a dead/immobilised June and Neville, Sheila for some unexplained reason decides to stay awake until the raid team enter WHF. Which is convinient for supporters.
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Obviously these are many obstacles in this account of how Sheila committed the massacre. But if these can be overcome, maybe there was a way for Sheila to have committed the massacre.
One option is to say Neville did not call the police. However only Sherlock and Holly from Red have agreed this did not happen. But never too late to amend. You're calls.