All that follows is purely Speculation:
It is my impression that MM was not fond of the kennels nor do I think PM was residing at Moselle. It's unclear where AM lived so I will speculate it may have been at Moselle. Why else would he be arriving there at that time of night?
I do believe the ones executed were summoned to the area for what, to them, seemed to be an innocuous reason.
Moselle is a hunting lodge. AM hunted ducks and tiny quail. Think if the target was larger. I also believe his sons, PM and BM, were excellent marksmen.
I've tried to imagine why the bodies were not close together but seeing the images we have of LEO on the property, surely the bodies were not far from one another at the kennels. Yes? Maybe PM was running when he was shot if his mom was first.
I cannot explain how they arrived at Moselle. By example, there were two vehicles registered to the law firm, att. One of them was towed but not the other one.
Can we assume MM drove one of the vehicles registered to the firm? Did she give Paul a lift since they were going to the same location?
I don't think there's a hired hit involved for the risks of being blackmailed are too high. However, I certainly could be wrong..