Why Did Macbeth Kill Macduff's Family

Asdescends
into insanity he becomes utterly obsessed with eliminating any threats to his power.  In
determining which threats to heedbecomes enthralled with all of the ideas thatgive to him,
believing that all of the their prophetic warnings will come true.  It is clear that Macbeth
seeks to eliminate threats to his own power due to the fact that he first murdersand his
children in order to ensure that Banquo's children will not pose a threat to Macbeth's rule (or
that of his familial line).  Moreover, in heeding the witches prophecy (who warn him of ),
Macbeth is required to take action against Macduff.  When thearrive to 's hiding place, they
seek to find Macduff himself, perhaps not fully aware that he has fled, and instead find the
family there.  They kill the family in part to eliminate the threat to Macbeth, but also to send
the message to Macduff that they will not fear him and that they believe him to be a traitor.
 Ironically, it is in this moment that Macbeth seals his own fate.  By murdering Macduff's
family he ensures that Macduff will retaliate and instigate an insurgency against him,
ultimately concluding in Macbeth's downfall.  This is the final act in the course of events that
guarantees Macbeth's eventual death.