I don't know but you need to get it under control. I have seen the damage these dogs can do. My brother got attacked when he was 6 years old he got 174 stitches in his head. The reason that dog did it was not known because they had 2 of them and the other St Bernard tried to help my brother by biting the dog and tring to get it off of my brother. It couldn't be because of the owners The nice one tried to help and anyone could love on this animal.Please don't get me wrong I don't think there is anything wrong with these dogs I have seen many of them that are great animals. I think there could have been something wrong with that one that no one knew about. Put your dog in an obedience class and see if it helps.
Nickie216 is right. ANY dog has the potential to bite, but you may never know the reason why. When you have a dog, you are taking the responsibility over anything that dog does. If you do not train them properly then you may end up paying a huge price if that dog injures or kills someone. Obedience training is KEY and if you are not dedicated enough to do it, then please find someone who can properly train your dog before something worse happens. Good luck, and make sure your dog is vaccinated for rabies! An unvaccinated dog that bites some one can be confiscated and sent off for rabies testing.
Saint Bernards have been overbred since the movie, "Beethoven." A huge demand for that breed occurred and careless, greedy breeders didn't care about the gentle temperament which is so characteristic of that particular type of dog. That overbreeding has caused aggressive, and less than gentle behavior. You have to safeguard other people from your dog's aggression or you could lose him. Good luck
Tastes like chicken...