It is sounding like to me that he returned to the apartment to get the credit card after the disposed of the boy, which is why her purse/wallet was found with blood. He still had blood on his hands, imo. To me, this indicates desperation for MONEY rather than rage toward his mother in general. Since it seem his mom wasn't giving up the money (assumption on my part), I'm thinking the reason he needed money wasn't for good reasons (such as caring for a child, paying a bill) but for bad reasons (drugs comes to mind).
So, my speculation is there was a violent encounter at the apartment. With so much blood, I'm guessing knife wounds. He transported her somewhere (my guess would be Bronx River, but that's just a guess), parked the car away from her apartment but close enough that he could walk back.
I am hoping the palm print in the car matches his print - and it's a slam-dunk to charge him with murder. At that point, I'm hoping he reveals where the body is. Until definitive proof, I don't think he will reveal because that knowledge implies guilt.
I absolutely hate thinking of her out in the elements. She must be found! (And, at this point, I do think it's "recovery" of the body rather than rescue. I would love to be wrong about that.)
jmopinion at the moment.