Something impossible happened-can u explain it

I was just playing on jpog and a rex raptor duel had just happened and i was just looking around hen a surviving raptor and a rex WERE IN A TERRITORY BATTLE!!!! Unfortunatly i just saw the end of it and i did not have fraps on so i just managed to see it
Can you explain it??

That's weird..Never seen that ever happen. Too bad there's not a picture of it.

I think that if you have donwloaded some kind of expansion pack, it may happen. I think that in GEP V.2 or something like that the Raptor-Rex death duel mod was included.