Who could of done this?

Duncan has been found dead. Macbeth just killed the chamberlain's and blamed it all on them. Will they believe it... Duncan's son's ran off scared to death. Macbeth has gone to scone and is now the new king of Scotland with Lady Macbeth as queen.
Macbeth is worried about the last prophecy about the witches(Banquos son will become king).
All he believes is that Fleance will take it from him and that just can't happen so he hires two men to kill off Banquo and his son Fleance. "Come, night, and blindfold the kindhearted day. Use your bloody and invisible hand to tear up Banquo's lease on life, which keeps me in fear." This quote is saying that Macbeth wants Banquo dead tonight and he'll do anything to keep the throne.
Now Banquo is dead but were is Fleance...
Gone he rode his horse far away and Macbeth is not happy. Because that prophecy may just come true because if the first three did then why not the fourth as well.