My dogs attacked each other yesterday, why?

Okay so, I have two Schnoodles (half schnauzer, half poodle.) They are VERY VERY friendly and neither of them have ever snapped at anyone or anything. But yesterday at my family’s Christmas party, my grandma gave them each rawhide “shoes”, as she always does when she comes over. Two times throughout the night, I had to literally pull them apart because the youngest one went to go attack the older one. At first I thought it was because one had stolen the others’ rawhide but as it turns out, both “shoes” were on the opposite side of the room. So what all of the sudden made my younger dog attack the other one? Now when I say attack I mean a ferocious, all-out dog fight, they definitely weren’t playing.