What should you feel when you kill a man? Guilt?  Only if you're a fucked up Christian.  Taking his hopes and dreams with a fifty cent bullet?  Bullshit.  If he has been tormenting you, it should be like swatting a fly, squashing a bug, stepping on a cockroach.  Because psychopaths are cockroaches.  They have no feelings.  They have no empathy.  They don't feel your pain and loss.  Squash them like a bug.  No regrets.  Just do it.