I'm very sorry to hear about your loss. I lost my dog last week while I was out of town. It was sudden too. She collapsed when my boyfriend was walking her. Unfortunately the vet couldn't do anything. I was devastated and could barely drag myself out of bed. I felt the guilt as well and constantly was questioning myself "what if?" Please know that your dog knew you loved him and that he is still with you in spirit. This group helped me and made me feel comforted in my time of need. There are also books available to help with the coping process. I know it hurts worse than any pain you have ever felt. The fact that it was so sudden is the worst. The rainbow bridge poem is also a nice read. I kept everything of Piper's, but put it away until I'm ready to see it. It was too hard seeing her bed and food bowl. My vet also gave me a nice poem with her paw print and her hair. I'm sorry again for your loss. We're here for you.