Foreknowledge and cooperation are concepts I have also considered. However, in respect of cooperation, how would he assist another individual who is experiencing a psychotic episode? That doesn't seem a credible scenario.
Was Sheila capable of loading bullets into the ammunition magazine, then attaching the magazine to the rifle, cycling a round into the chamber, and pulling the trigger? I have to believe that she was. Could Sheila, therefore, reload the gun when the bullets ran out? I'm afraid I believe that she could. Was Sheila capable of screwing a silencer onto the thread on the end o0f the guns barrel? Yes, I have to believe that she was capable of doing this. Was she capable of unscrewing a silencer from the guns barrel? I have to believe that she could have done that if needs be. Could she have used the loaded rifle during a psychotic episode? Yes, I have to believe that she could have done precisely this, or that. Who trained her to use the rifle? Who trained her to load bullets into the guns ammunition magazine? Who taught her how to cycle a round from the magazine into the breach? Why, of course, we all know that Jeremy had given his sister lessons in the art of all these activities. Even a relative testifies to being told by June Bamber that Jeremy had been teaching Sheila how to use the rifle...
Jeremy taught Sheila the art of loading and firing the rifle, it was a reckless thing to do considering Sheila's mental health problems. Sooner or later, Sheila might put to use the skills Jeremy had taught her. Jeremy should never have introduced his sister to the gun. Maybe he secretly hoped that one day she might go berserk and kill one or other, or both of her parents. Do I believe that a person who has the skills to load and fire the rifle, loses that ability in a psychotic episode? No, I believe the skill is not rendered inactive - there are many cases where a person suffers a psychotic episode, yet shoots his/her victims, or stabs them to death, so on and so forth...
Jeremy trained Sheila to load and use the rifle, I believe this amounted to his involvement in the tragedy. Once he received the call from his father, informing him that 'Sheila has got the gun, she has gone crazy', maybe Jeremy secretly hoped that she had fired it, killed somebody, maybe she might kill everybody. Maybe that's why he took his time, phoning Witham police station, and later Chelmsford police station? Maybe, when he phoned Julie at about 3.30am, and told her, 'there's something wrong at the farm', he simply said that half hoping that his sister might kill them all...
That's the way I see it, Bamber himself was not physically present at the farmhouse when his sister sank into a psychotic episode, and started to use the gun. He didn't need to be, his sister was competent using the rifle. She could load it, fire it, and reload it if needs be. He had trained her well in the art of the gun. The longer his sister remained in possession of the gun with access to bullets, the greater the possibility that she might be capable of killing everybody inside that farmhouse...
'There's something wrong at the farm', Jeremy. Julie, 'go back to bed'...
