The proper steps should be in your bylaws.  Can you find a copy of those?  I can tell you, though, that this process is almost always a very messy one that can derail the good work of your PTO for a long time.  Have you tried other steps first?  Have folks approached this leader (at a time other than in the midst of chaos) for a discussion?  Is there a way to make things work until the next election?  Etc.
         - Rockne
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