I am so very sorry for your loss. I understand the shock and grief you are feeling. I lost Max suddenly in November when I took him outside to potty and a coyote grabbed him and killed him. It is so hard getting over the shock and then the guilt and "what if's" - just remember how much love your dog gave you and the memories will help comfort you. My thoughts are with you. Please feel free to email me if you need to talk.
Jackie