I'm stuck at the blue raincoat.
He must have put it on at the house, before going to the kennels. Had the rain started? He wanted to protect his button-down (seen in the earlier tree video) and just happened to have it on when a sudden need to kill arose? Or it was very intentional.
What was Maggie wearing? Did AM have the only rainwear in the group? When did he acquire it? Had anyone ever seen him wear it prior?
Did Alex have the prepared dinner? Did he mention his workmoneytroubles to Maggie? Then throw on his raincoat?
How will the inevitable television series present that final +/- hour?
The missing weapon. Is it missing because it has Paul's fingerprints on it? Did he attempt to wrestle it from his father, perhaps resulting in the catastrophic head wound when AM got control of the weapon?
On the jailhouse, is AM still chatting it up with family members? Holding court, as it were. Does NOTHING drop his ego down a peg? How is there even room in his small cell for his big head?
Blanca prepared the last meal the victims enjoyed at Moselle. Stomach contents of mother and son were similar at autopsy.
It rained lightly off and on during their visit. Alex's not wearing the bleu raincoat during the tree video. I think it was inside his truck that was parked near the kennels.
I'm not sure who was was using the water (water hose) but we hear water splashing on the pavement when Paul is at the kennels with the brown lab. Therefore, we know it wasn't Paul using the water. It could be that Big Red donned the bleu raincoat before performing, perhaps, the task of rinsing a kennel as a cover so as not to wet his clothes but, more importantly, the bleu raincoat was worn to keep blood spatter and GSR from getting onto Alex and his apparel.
Perhaps he had gloves tucked inside the bleu raincoat pockets so GSR and fingerprints would not be present. Cold and calculating heights of Evil.
Currently, I cannot conceive of anything short of AM performing the murders as steely as would an expertly qualified and determined hitman who would monetarily benefit from the deaths of Maggie and Paul. The husband and father was their assassin.