Conversation so far:
who wrote the note to bree on desperate housewives
It is revealed that it was Orson Hodge who wrote the letters to Bree Van de Kamp.
what is the relationship between bree van de kamp and orson hodge on desperate housewives
Orson Hodge is Bree Van de Kamp's second husband.
who was bree van de kamp's first husband on desperate housewives
Rex Van de Kamp was Bree Van de Kamp's first husband.

Question: How did the marriage end?
Self-contained rewrite: how did the marriage between bree van de kamp and rex van de kamp on desperate housewives end