I am so sorry for your loss. Please never again use that vet. A puppy should never have food/water withheld from them except right before surgery. After surgery, I've always had food and water accessible for my dogs.
My heart goes out to you, I can't even imagine what you're going through

I am so sorry for your loss. you had a very young puppy, that should have been with it's mother and littermates until 12 weeks old. Such a little, one, and yong Young Yorkie can be fine one moment, and then become very ill quickly, then expire. My guess would be it was low blood sugar that took the life of your puppy. I have no idea why the vet wanted you to with hold food. That can't be done in such a young Yorkie pup.
What you and your family went through is heartbreaking.

I am so very sorry for your lost. I can only imagine what your children are going thru. Hugs.

Dear all, thanks again for your support.

I am still trying to find answers to my questions.

1. The seizures developed almost immediately after the antibiotic shot. But the vet injected a glucose too, at the same time.
That's why I don't understand how hypoglycemia could developed from that point?.. And only 2 or 3 hours passed after he had his last food when we arrive to the vet clinic.

2. The first symptoms was gagging or coughing. I even cannot explain exactly what was that but it was a reason why we went to the vet.
Perhaps, it looked more like a Kennel cough, I checked youtube and found it very similar to those sounds and movements that my puppy had.
Could those symptoms be low blood sugar symptoms?

3. I did some research and at I have a two month old yorkie...after a couple of days from... I found a question describing a situation very similar but there it was said that the diagnosis was a distemper.
"I have a two month old yorkie...after a couple of days from bringing her home from the sore where i purchase her; she became sick by gagging...so i took her to the vet and it is distemperment..which we are treating now...will she be okay?"

I am just thinking if it is possible to have a distemper after getting a vaccine just a week and half ago?

Did someone have this experience??

Could those symptoms be just symptoms of a distemper but in light form of disease because of vaccination?

Sorry for a lot of questions. I think that if I understand a situation clearly this will help us to avoid more mistakes in future if we ever decide to have one more puppy...:(