Everyone, thank you for the comforting words.
The post mortem revealed that my dog's right lung was filled with blood. He had a bruise on his right flank, centered on his rib cage, yet he didn't have any broken ribs. Somehow the trauma was carried through to his lung, which then filled up with blood.
I am not clear on what finally cause him to leave us, or how long he had the injury. I don't know if he suffocated.
I think what I do know is that it was not from natural causes, but instead by a human hand (maybe a car).
