Why does one of my cats keep attacking the other one?

United States
@Bd200789 (2996)
June 10, 2008 6:05pm CST
The cats have never fought like this until now. I was on the computer when I heard this weird noise. One cat was growling at the other and biting his neck. Midnight hadn’t done anything. He was fast asleep! I had to separate them. This has happened a lot in the last few days, and I don’t know why. They are both tomcats, and about a year old. Is this normal?