I don't know about the Puget Sound but the Quileutes told me that they killed off all the brown bears when they first colonized because they were in direct competition,, that was on the Coast/OlyPen... I was guessing about 10,000 years ago,, but could have been longer or shorter...

I believe I read somewhere that there weren't any "historical" (read white) records for grizzlies on the OP. So, the could have wiped them out. Seems odd that no other tribes seemed to extirpate them but given that the area opened up so recently they might have had only a few to remove.