In Act 3.1 why is Macbeth frustrated that he killed Duncan in regards to Banquo's fortunate prophecy?

Macbeth is pretty agitated that he killed Duncan so that, according to the witches, Banquo's "issue" or sons will become kings. Macbeth only wants his line to be kings even though he doesn't yet have a son of his own, "for Banquo's issue have I filed my mind."