My 1 year old shih tzu was running frantically through the house and collapsed on the floor and urinated on himself. What happened?
What could have happened is that your dog got an epileptic fit and collapsed. Another cause could be that your dog fainted as a result of excitement or a heart condition. However, you should take the dog for check-up to get an accurate diagnosis.
It could have been a seizure. Get him to his vet ASAP.
He's either sick or injured .. I am assuming you checked him out. Could he have had a seizure?
Maybe he was scared? tell if he's okay later today! :)