Mat 5:21 `Ye heard that it was said to the ancients: Thou shalt not kill, and whoever may kill shall be in danger of the judgment;
Mat 5:22 but I--I say to you, that every one who is angry at his brother without cause, shall be in danger of the judgment, and whoever may say to his brother, Empty fellow! shall be in danger of the sanhedrim, and whoever may say, Rebel! shall be in danger of the gehenna of the fire.
Mat 15:19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies...
Mar 7:21-23 For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, Thefts, covetousness, wickedness, deceit, lasciviousness, an evil eye, blasphemy, pride, foolishness: All these evil things come from within...
Murder is in the heart. Does it matter if there was not one there to be murdered? Does it matter even today among people? If I am prowling the streets looking to murder someone, surely I am a murderer by Jesus' declaration, if only "to be angry without cause" is to do.
1Pe 5:8 Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour...