Did Louis rape mom?
I think it's kind of odd that they invested so much into the back story of Louis' mom getting raped as a house showing as the explanation for him carrying a knife, but never went further with it. First off, if you work in real estate and are rich, you can probably get a gun permit, even in LA, as some kind of bonafide occupational risk, with the rich part greasing the skids.
I wonder if there wasn't some unexplored angle where Louis actually raped his mom, as part of a twisted-rich-people family sickness dynamic. I don't think Dad was ever mentioned, but it totally makes sense that once dad dies, sicko Louis takes his place and cements his control by having his way with mom.
Mom is a rich, victimized co-dependent basket case who takes the abuse and does everything to protect her son, who she knows is sick. This helps explain why she kills the PI and tries to kill McConaghey at the end -- the ever-protective mom trying to shield her son, and ultimately, the shame of her twisted existence.