What is Jack's new "compulsion?" How do you explain it? Is it like any compulsion you ever had?

Jack wants to kill something in a bad way. This goes beyond hunting for meat. Jack experiences this primal longing to inflict his will on to another living thing. I suppose this is something primal, that Golding, believes lives beneath or collective hunter/gatherer DNA. No, I can't stand hunting but I have been really angry at people but certainly would never act on any violent thoughts.