To put it more crudely "no sex life".
Clearly he was so inept at finding things to enjoy in life that the only way he felt that he could be O.K. again was to murder a bunch of people he had never met and knew virtually nothing about. People reduced to objects - that is one of the sigils of psychopathy - objectifying people so that they are no longer worthy of empathy or understanding or good things of any kind.
The impulse to murder in this way (psychpathic) is described by the few surviving genuine psychopaths as a feeling very similar to that of (forgive me) taking a crap.
The individuals feel that they must do this thing or they will never have relief. Like someone who needs to take a crap.