Macbeth's emotional state immediately after he kills Duncan is one of shock, horror, and regret at what he has done. He is overwhelmed by guilt, fear, and disbelief at his own actions. Some key quotes that highlight Macbeth's emotional state:
MACBETH: Awake, awake! Ring the alarum bell!
Murder and treason! Banquo and Donalbain!
Malcolm! awake! Shall Romeo command?
Or needful fight defend?- Wake up! wake up!
Shake off this downy sleep, death's counterfeit,
And look on death itself! up, up, and see
The great doom's image! - Malcolm! Banquo!
As from your graves rise up, and walk like sprites,
To countenance this horror! Ring the bell. [Rings the bell]
He is clearly in a panicked, agitated state full of distress and regret. His actions have awakened feelings within himself that he cannot control or understand. He realizes he has crossed a line into darkness from which there is no return.