Final answer:
Banquo suggests discussing King Duncan's murder later, when they can speak freely. He is likely cautious to not make accusations without evidence and for fear of reprisal, aware of the witches' prophecy hinting at Macbeth's possible motives.
Step-by-step explanation:
Understanding Banquo's Reaction to Duncan's Murder
Banquo suggests they stay calm and discuss the tragic event of King Duncan's murder at a more appropriate time, when they can speak their free hearts to each other. He does not directly accuse Macbeth because he may be cautious of making unfounded accusations and is aware of the prophecy that the witches told Macbeth, which may cause him to suspect Macbeth's ambitions but without concrete proof. Moreover, Banquo could be concerned about his own safety, knowing that voicing such suspicions could be dangerous in a court where the murderer has just been bold enough to kill a king.
Despite Banquo's suspicions and his indirect mention of the witches' prophecy that could incite Macbeth to commit regicide, he opts for a diplomatic approach. Banquo's line 'That trusted home Might yet enkindle you unto the crown, Besides the thane of Cawdor' hints at his doubts about Macbeth's involvement, yet he chooses to keep his thoughts to himself at this stage. His caution and foresight are indicative of his awareness of the tense and precarious situation.