"Child of God/mass murderer" is an OXYMORON. Preachers who teach, "go out and live like the devil all you want, no big deal, you will still be saved" are deceived. Those who are born of God do not want to live like the devil (1 John 3:7-10).
I get tired of certain people in the NOSAS camp who try to place EVERYONE who teaches OSAS in the same camp as these "license to sin" deceived preachers.
If someone who attended my church and claimed to be a Christian went out and committed mass murder, my Pastor would not be saying, "he will be saved anyway." My Pastor would say, "obviously, that guy never truly received Jesus." I would say the same thing.