In this scene, the characters find out that King Duncan has been murdered. The audience knows that the man responsible for this was Macbeth. However, the characters do not know this.
Upon realizing the tragedy that happened, the characters are in shock. However, Macbeth reacts quickly and immediately kills the guards. He claims that he could not contain himself. However, this is an error in judgement, as it brings attention to Macbeth's odd behaviour. Moreover, as a consequence of this, Lady Macbeth suddenly faints. The viewer knows that such odd behaviour from Macbeth and Lady Macbeth are a consequence of their guilt.
On the other hand, Malcolm and Donalbain are worried about being blamed for the murder, so they decide to flee.
