i had a rottie that did that once sebastain was barking like crazy and would not stop so i got up to see what was up Nala my rottie was laying in the hall and he was barking at her right in her face i said Nala whats wrong she didnt move i put my hand on her ribs and shook her she still didnt move i yelled her name again and again and when i touched her she felt stiff and cold i freaked out and started crying and yelled to my son OMG nala is dead he came out of his room and said nala and she looked up at him i couldnt beleive it i was so upset. After everything calmed down a little i thougth geez what would i have done with an 80 pound dog at 3am