There is objective evidence that establishes how the murders were carried out.
Such objective factors include:
A) The location of bodies
B) The locations of bullets that exited/grazed victims.
C) The location of spent casings
D) Trajectory of wounds
E) nature of wounds
F) blood evidence
G) other considerations relevant to the weapon including reloading issues
H) other considerations relevant to how people would act
The totality of the evidence establishes the shooting commenced in the master bedroom. At minimum a full magazine (10 rounds) was discharged in the opening attack. A total of 11 rounds were fired into the parents in the bedroom. It is possible to load 11 rounds into the weapon so theoretically possible for all 11 to have been fired in the same sitting though it is highly unlikely.
June was shot at least 6 times in the opening attack. June was shot with 3 different arcs of fire. She was lying down in the bed at the time the attack commenced. This is the first arc of fire, the killer was at the foot of the bed and angled towards her side of the bed thus angled towards her right. The trajectory of the bullets as well as the location of the casings and blood confirms this. 4 shots were fired into her as she way lying on the bed. 1 round hit her head above her ear leaving blood on her pillow which reveals her head was in contact with the pillow and bleeding on it. Her right knee and right forearm were also hit as she was lying down in bed. Both bullets exited her and ended up in the bed. The final round of arc 1 hit the right side of her neck as she was sitting up. We know she was sitting up because the bullet went down and exited her back ending up in the bed. If she were still lying down the bullet would have traveled upwards like the other 3 instead of down.
The second arc of fire was to the right side of her chest. She was hit in the chest as she was getting out of bed or just as she got out of bed before she had a chance to fully turn and face the killer. The 3rd arc is a single shot and it was the one between her eyes.
This diagram shows the 3 arcs. The red lines shows the trajectory of the shots while the yellow shows where the casings went. The casings roughly eject between 2 O'clock and 2:30. I didn't show one for the shot between the eyes. The casing on the transition strip is associated with this shot it bounced off the open door landing there.

The shot between June's eyes was delivered quite a bit later than the first 6 shots. We know this because blood evidence indicates she walked all the way around the bed to Nevill's side and then back towards the door before the final shot between her eyes was delivered.
It is possible that the killer fired the first 6 shots in a row. It is equally possible that after the first 4 shots the killer targeted Nevill and then after June got up turned again to fire arc 2 (the shots to her chest). There is simply no way to tell for sure. Logic suggests that the killer would not want to allow Nevill to come attack the killer so would want to turn and target Nevill after firing the first 4 shots.
Nevill was shot 4 times total in the bedroom. At least 3 shots were fired while he was sitting up in bed or in the process of getting out of bed. He was targeted from the left side. His lip, jaw and shoulder were all hit while he was sitting or in the process of trying to stand and not fully upright. We know he was not fully upright because the trajectory of the wounds were downward and it he were standing upright then the rifle would have to be pointed up to achieve such entrance wounds. Casings would land either on June's side of the bed or the floor near her bed in a similar area to where the casings from the shots to June in the bed were. One such casing was on the bed. It is possible there were more but June knocked them off onto the floor when she got up.
The last wound to Nevill was a graze wound. It's impossible to know whether he was fully upright or not at the time. It was in a location where it could have been achieved while he was fully upright.
After the gun was empty the killer retreated to go reload the weapon and Nevill followed to try to stop the killer or there was a small physical altercation, during it Nevill got by the killer and decided to go to the kitchen to try to arm himself.
The killer was firing at the foot of the bed so unless the shooter retreated to reload Nevill would have to fight his way through the killer to run to the kitchen. Similarly, June would have to fight through the killer to walk to the other side of the bedroom.
It is possible that after the gun was empty both parents ran to the killer and there was a brief scuffle and this is why June walked to the other side of the room. The killer may have punched June there were injuries that could have resulted from such. This ganging up could be why the killer retreated to reload. It is also possible though that Nevill got around the killer and ran to the kitchen himself with the killer following. We have no way to know for sure whether the killer left the room before June walked to the other side and back or whether she tried to fight the attacker with Nevill.
Nevill left blood on the wall so either he was pushed against the wall by the killer or fell himself as he was trying to get to the kitchen. It seems probable that if the killer had been chasing Nevill that the killer would have caught up with him before he got in the kitchen and they would have struggled in the hall or on the stairs. It seems to me more likely that Nevill was chasing the killer and caught up with the killer in the kitchen as the killer was trying to reload. Regardless of who was chasing whom, in the kitchen is where they struggled.
As they struggled the light lampshade was broken, the mantle was damaged, furniture was crashed into and crockery knocked to the floor. Nevill was beaten with the butt of the rifle until he was unconscious. He tried blocking blows with his arm resulting in numerous abrasions, but eventually the killer bashed his head in rendering him unconscious. In the process his watch was torn from his wrist and part of the butt sheared off. The shearing and other cracks as well as the injuries were indicative of the back of butt being bashed against Nevill. There was also back spatter on the butt of the rifle.
After Nevill was unconscious the killer was able to put the gun down and to safely reload the magazine. The killer then shot Nevill 4 times in the head killing him. The shots were fired in 2 pairs. Either pair would have killed him. One pair was to the top of his head the other pair the right side of his head. Only 3 casings were found in the kitchen. The last casing was found on the landing. It stuck either to the killer's shoe or a raid team member's shoe and was transported to the landing where it was kicked into the corner where the carpet met the wall.
Some try to suggest that Nevill was shot in the head while running down the stairs. This is not true because he would not have made it to the kitchen if he had been shot in the head prior. Moreover, the shots to his head were in tightly grouped pairs. Also any casings would have been on the ground level near the stairway or on the first few steps. After all that happened the killer was not happy with the lethality of the weapon so that is why 4 shots were fired into Nevill's head instead of just one.
After Nevill was killed in the kitchen then the killer ejected the magazine and fully reloaded it. Most likely this resulted in 11 rounds in the weapon because 1 was most likely in the chamber already.
Some suggest the boys were killed first because they were in their beds asleep but this makes no sense. The greatest threat was the parents so they would be killed first. Moreover, if the boys were shot first that would have left fewer than 10 rounds in the weapon and 10 rounds would not have been fired in the master bedroom. The suggestion that it is worse to risk the boys waking up from shooting the parents than to risk the parents waking up from shooting the boys is absurd.
The killer returned upstairs and fired 3 rounds in rapid succession into one boy and 5 rounds in rapid succession into the other. The killer was still smarting from the prior inability to easily kill Nevill so this time fired multiple head shots just like had been done to Nevill in the kitchen. The 9th round was fired between June's eyes to make sure she was dead because again concerns about the lethality.
The gun had 2 rounds remaining and these were used to shoot Sheila hence the gun is empty. She was shot while seated propped against something. The shots were angled right to left. The killer was holding the weapon to the right of her. The first shot was almost level and at near contact range.
After the first shot she put her arm to her neck trying to plug he wound. Blood leaked onto her outer palm and down her wrist towards her elbow. The killer then jammed it under her chin and fired again.
Her blood initially leaked down her neck onto her shoulder and down her arm and the side of her breast. Her body was dragged flat and then the direction of blood changed to going down the side of her arm and side of her neck. 2 small trails that ran down the side of her arm leaked onto the Bible. The Bible was then picked up for some reason. A pool of blood formed from the blood that ran down the side of her neck. The Bible was placed in such pool of blood. When placed there the 2 lines that ran down her arm no longer lined up with the lines on the Bible. Why it was moved is unknown. Maybe while staging the gun on her or further staging her body it closed so had to be reopened. That actually would make the most sense and make the killer least stupid.
Scenario:
Killer moves Sheila flat in order to plant the rifle on her. Killer opens Bible getting some blood on it from his gloves and places it against her. Blood running down her arm gets onto the Bible. While trying to stage the rifle the Bible closes. Killer reopens it to same page. The mirror image was created by it closing and being reopened. While killer is looking for the same page to reopen it to the pool of blood forms from her neck. The killer puts it back not too far from where it had been but not exactly the same spot so the lines from her arm and the Bible don't line up exactly. Moreover, by this point in time the pool of blood has formed and thus the Bible is placed in it.
This scenario makes far more sense than the killer repeatedly opening and closing the Bible and repeatedly moving it. This is not too different from a suggestion Holly made a couple of days ago.
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