I can't say whether he's possessed or not, but I can say based on what you have said is that he is a narcissistic sociopath. He needs help, abusing animals and having no empathy or regard for others is the one thing all serial killers have in common. The one thing he lacks in the cocktail is some form of abuse. Do some research on the science behind criminal profiling it is fascinating and disturbing.
I do believe the devil can posses people but its just not as common today as it was in the past.

