My first guess was something like a brain tumor making him hear voices and changing his behavior, but:

two other suitcases were found, also with human remains, nearby along the intracoastal

and

police searched the apartment where they found evidence of a grisly crime: blood spatter throughout the home, cleaning products with blood on it, drag marks and a large amount of blood in the living room, dining room and master bathroom

I’m no criminal psychologist, but that doesn’t seem like the behavior of someone mentally unsound (well, aside from the serial killing, anyway).