I was hiking with both of my german shepards, suddenly the younger one (7 months old, about 50 pounds), laid down and couldnt keep going. I put him on my back and started the descent, but after 10 minutes, he started vomiting a yellow/brown liquid and began faiting. Then I started running with him on my back, but after a while he stopped moving and i realized he couldnt breathe anymore. The temperature was very hot(about 32 degrees Celsius 90 Farenheint), but i kept him hydrated by giving him water every 20/30 minutes, what couldve happened?