Analysing of No country for old men

From the beginning of the film the main character has been a mystery on who he is and how he really is. They never showed his face until they got to the police station when we first saw him kill the officer. This really set the tone for who he really is. After killing the officer he took the police car and pulled over a normal citizen and walked the car very slowly and casually then killed him. Just before he killed him he said every thing was going to be ok but it wasn't. Then killed him by using a gas canistar. This gives the impression that he gets pleasure by killing people, because after killing the two victims he had a little grin on his face and this ringed alarm bells on the type of guy he really is. Which is maybe him being psycho or having a mental problem.