In the story Things Fall Apart, why did Okonkwo kill himself?

Throughout
the whole novel,struggles with the changes taking place in his tribe.  He is initially known as
one of the strongest, most honorable tribesmen, but as the white man begins coming in and other
tribal members begin to change as a result, particularly his own son, Okonkwo cannot handle the
change.  He sees these other clansmen as weak, like he saw his father was weak.  The one thing
Okonkwo fears the most is weakness.  By novel's end, Okonkwo has tried to remain strong against
the tide of change, but he appears to be the only one.  When he kills the colonial official in
the...