answer from former IMDb:

"Whilst Sam wasn't anywhere near as bad as Josh and Bobby he chose to pretty much turn a blind eye to the things they were doing in order to not get on their bad side. Eva is the one who tries to defend Marilyn when Josh and Bobby take her back to their room and it ends up being Adrien who pretty much looks out for Eva whilst Sam seemingly turns a blind eye to what Josh and Bobby were doing.

Sam keeps getting wound up by Bobby and Josh regarding Eva's feelings/relationship with Adrien to the point where he tries to rape her and ultimately it's Adrien he kills when he gets hold of the gun. Now think about that, he has the gun and the person he chooses to kill is not one of the guys who have raped, tortured and killed a woman but the guy who has made the mistake of trying to defend someone you love to the point where you become jealous about it because you don't have the balls to be the type of man he is.

As for Mickey, I think he had no intention of making it out of that basement anyway. When he told Eva about there being another way out he didn't say 'We'll be making our way through some god awful beep but 'You'll be making your way through some god awful beep Mickey wasn't dumb, he knew there was only one suit and I think by the time he told Eva about the other route out he was ready to die but wanted to give Eva the opportunity to leave as she was the only one out of the whole group that he eventually came to like and had respect for.

His reaction when he realises that they've been locked in isn't to start cursing her but to laugh and have a smile on his face as if to say 'I knew the girl could do it!'. I think he respects her survival instinct and knows deep down that she has made the right decision in going it alone and if he had the chance he'd have probably done the same thing."