So I have just finished my coloseum. The first time I used it everything worked as expected; monsters appeared and my novice military (which was stationed on the coloseum) slaughtered them. The problem came when I started a second fight with the desert creatures. One of my dwarves died so I immediately went to check the combat reports to see what happened. I was shocked to find that one of my axedwarves apparently decided the now dead recruit was really an arena monster and had been merrily hacking away at him. Of course, this turned into a full blown loyalty cascade, which was expected after the first death, but I can't for the life of me figure out why the axedwarf turned on his comrade to begin with. Anyone have any explaination for this?
EDIT: Side note, the loyalty cascade devastated the fort. Went from 138 dwarves to 3. The beserk mayor, a starving dehydrated very unhappy recruit who refuses to leave a pond outside the fort and another recruit who just got maimed by a tame bone mammoth. BTW do loyalty cascades affect livestock too? I swear this bone mammoth and a woolly mammoth (both tame) were fighting earlier.