An overwatch action automatically targets whoever walks into range first, and the leader of the mutants was at the back of the squad, requiring the other guys to be shot down before he can be targeted.   You can choose to designate an overwatch action as "leaders only" or some such thing, but because of the way the squad rules work, the defender gets to choose who takes each hit from autofire or squad attacks.  (to save time in abstract fights, mostly)<br/><br/>Tactically, it would probably be a better move to have the leader at the front, since he can soak a LOT more shots and the other men have more firepower, but the Chaos mindset isn't genial to that sort of behavior.  (the leader is too selfish, and the minions would likely shoot the leader in the back if they all had the chance)<br/><br/>I rolled your dice for you to save time, but if you'd prefer to roll all your own dice, I can respect that.<br/><br/>As for the confusion, I assumed that Delila had joined you in watching the chokepoint, figuring it would be safer than joining an assault.  As for Cortez, that's just general purpose confusion on Someguy's part.