Macbeth's murderous rampage begins with the murder of Duncan, Macbeth having apparently agonized over the injustice of actually killing him. It seems that, having recognized Duncan's "faculties so meek"(I.vii.17) and the fact that he is Macbeth's kinsman" (13), Macbeth's initial decision to "proceed no further in this business"(30) is soon undone by the intervention of Lady Macbeth as she makes him feel that he is not a man - "When you durst do it then you were a man." (49)
The guilt begins to consume Macbeth even before Duncan's actual murder. Shakespeare prepares the audience and foreshadows events that are to follow. An indication of the "fair is foul" is the apparition of the daggers which completely confuse Macbeth. Having been so affected by the witches "cannot be ill, cannot be good"(I.iii.131), it seems Macbeth's guilt is misplaced and it is actually the fear of being caught - "false face must hide what the false heart doth know" (I.vii.82) that sends him into a frenzy. Macbeth is still capable of rational thought and the daggers are "a false creation" (II.i.38) although they are "palpable". The ringing of the bell is Macbeth's cue and he commits Duncan "to heaven or to hell."(64)
When Macbeth returns to discuss the events with Lady Macbeth he is distraught but Lady Macbeth tells him to "consider it not so deeply."(II.ii.30).Macbeth however, cannot reconcile himself as "Macbeth does murder sleep."(36)He has even forgotten to leave the daggers behind. He does realize what he has done as "all Great Neptune's ocean" is unable to "wash this blood Clean from my hand"(60). He is calmed by lady Macbeth as she tells him that "a little water clears us of this deed."(67)
He has also murdered Duncan's attendants so that they can be blamed - " I do repent me of my fury that I did kill them"(II.iii.105). It is Macbeth's fear of exposure that overwhelms him.