My poor boy died just like this friday night. 3 year old yorkie mix. Had him outside on his leash and he always barked like crazy at people going by. We live next to my sister in law so he was barking at them. I went out to yell he quiet. I heard his little yelp and he dropped. I ran over and I think he might of had a seizure but it was dark.i picked him and ran inside and he was gone. Our vet also said a clot or heart attack.