Which actions by Macbeth portray his mental state in act 2?

The key turning point of the play, and of Macbeth's mental state, occurs in act 2: Macbeth's murdering of King Duncan. Even before the murder, we see that Macbeth's mind is tormented by visions, as he sees a vision of a dagger he believes is guiding him to Duncan's chamber, where the king sleeps. After the murder, we see that Macbeth feels very guilty, as he refuses to reenter the chamber, "afraid to think on" what he had done. The vision of the dagger presages some other visions Macbeth sees, most notably the ghost of the murdered Banquo. Later in the play, it becomes obvious that these apparitions are the product of Macbeth's guilt, which he quite clearly articulates in act 2. Over time, however, he becomes hardened, essentially self-absolved of all guilt for the murders. He becomes a monster with no conscience whatsoever. We see in act 2 that this is not yet the case, which makes his descent into what modern readers will recognize as sociopathic behavior all the more dramatic.