Jesus of the bible is not adequate to forgive the sin of murder.
Murder is not an easy thing to repent of, and often if not always does not complete in this life. Luke wrote that David was still in hell and had not yet ascended to heaven. See http://www.lds.org/scriptures/nt/acts/2.26-38?lang=eng#26
If your point was that “once saved, always saved”, you need to work on your communication skills.
Unrepentant murders are not saved (I feel safe saying that)
Delph