Phone Call
I believe such a phone call did take place from the scene by Ralph to Jeremy, but what I am not convinced about are the actual words which Ralph used - Did he actually say to Jeremy, "Sheila has got the gun, she has gone crazy, come quickly", or did Ralph say "She has got the gun, she has gone Crazy, come quickly"? And more importantly, if Ralph did use the term "She" as opposed to "Sheila", who might Ralph have been referring to? Sheila, or June? It is easy to understand how Jeremy could have been mistaken into believing that his father had used the term "Sheila" at the time, because she had very recently been discharged from hospital, but equally with the benefit of hindsight he could have been referring to his wife, June...
I am not convinced that Ralph was talking about Sheila at that stage, since it is just as likely that he was referring to June, who also had a history of mental illness...
You only have to look at the way Jeremy was questioned about this call when he was arrested and interviewed to see how the situation could have developed regarding what his father actually said, what he (Jeremy) thought he (his father) said, and what Jeremy told the police what he (father) said, and what the police recorded what he (Jeremy) said his father had said? For these reasons I do not think anyone can reliably say that the call did not take place, and that it was just an invention by Jeremy to try and get away with the perfect murder(s) because he had already killed everyone by the time he called the police, and because the police were now saying Sheila did not take her own life, the phone call must be made up?