ok my turn....

Third
night time falls,
We go out and hunt
my prey tries to flee
he will not go free
I ask " If you don't want me, why did you make me?" 
he laughs, I end his life
Ross tells me the creep is through
I leave him, he who is my love
not a crook, not a cop 
not a girl, what am I?
I am a third.