I really do think it was premeditated. I think that's why he's holding on so tight to his story. If it was purely an act of rage, I think he'd break down easier. The circumstances make me think premeditated as does his demeanor since, but I really think he decided to do this and felt completely justified, entitled, to do this. Therefore, he still does. If it were an accident, he wouldn't hold that position so strongly. he'd waver more easily. He did this to serve a purpose, and he feels justified in that purpose. it is serving its purpose and so he believes he did what he had to do for himself. I also think the actual murder was an act of rage, with alcohol. How else could you do something so horrific? But it was planned. I feel sure that he followed his plan to the Tee from the moment DR arrived. I've always thought that he did it the first night as to avoid feeling a bond with DR over a couple of days of hanging out together. He could depersonalize DR easier the faster and sooner he did it.
and I think the "praying" to DR is b/c MR believes DR had to be a sacrifice for his own agenda. he's probably sorry that he had to be a sacrifice, and he's probably says he's sorry in these prayers to DR, and asks for forgiveness, but not b/c he's remorseful. He just wants DR to understand why he had to be a sacrifice for MR's agenda, which MR still holds as the most important thing.
lease:
