death of our shepherd

[JaneyCH]

My fur baby Myma passed away today unexpectedly.  She came upstairs this morning around 6:30, went outside to pee, then came back inside, got her treats, and went back downstairs where she has the entire area to herself while we work.  When my husband got home (I was home sick today) around 4:15, I called for her, but she did not come.  When he went down, she was near the stairs, completely stiff.  There was blood at her mouth and her jaw was clamped tightly. Until this morning she had no other problems other than hip dysplasia, for which she was receiving glucosamine every morning.  She did not eat her dog food yesterday but she did eat some of the cat's dry food this morning.  She had been drinking a lot of water the past two days. She did not give us any sign that anything else could be wrong.  In fact, around 10 I was downstairs playing with her for a few minutes and she seemed fine. Loving as always.  Now I am trying to figure out what I didn't see,  She began coming out of rigor around 5:30.  The best I can figure is she passed away shortly after I saw her last, but I don't know and it's hard to deal with.  She was almost 11 years old.  I thought we'd have her a few years more.  Any ideas of what happened to her?