My mother-in-law was taking him for a walk when he started foaming out the mouth and losing control of his bowels. She was able to get him back to the house where he was very lethargic. I was able to get him to our family vet within 10 minutes. We waited about 10 minutes to be seen. During this time our dog seemed to be fine but was breathing short, through his mouth. He went back to have blood work done and when they got ready to do his chest x-ray he went into respiratory distress. A few minutes later his heart just stopped. Any idea what might have happened? He showed no signs of illness up until his walk. To my knowledge he was not exposed to any chemicals. Before death he had a silvery substance on his skin/fur that rubbed off on my hands, almost like an oil?!