Dog attacking another dog?

My roomates have a few dogs. The main dog I am talking about is a grand champion pitty. He attacked one of her dogs, another uncut male. A few weeks later, he attacked another of her dogs. this time a female, which resulted in her death. This week he jumped on the puppy, also an uncut male, usually these 2 get along great. As a matter of fact they were both hanging out all day long together, and then all of a sudden the champion just grabbed the puppy up. My question is: Is it normal for a dog to keep getting into fights once they get into one?