Actually, I will say I don't know what blame the hotel/casino may or may not have as I wasn't there nor have I heard the testimony or evidence around the whole situation and I doubt you have either. This is, and should be, a decision for a jury and IF there is something that the motel/casino did or should have done why shouldn't they share some of the blame?
While we may disagree about the hotels' ultimate potential blame or if they could have done something, at all, I do believe suing those that were targeted and had absolutely no blame, at all, is horrible even if it is to shield themselves from blame or lawsuits. Yes we live in a litigious society but taking advantage of innocent people who have been horribly attacked and already shot or injured rather than proving you do not have any blame or contribution to what happened is not the way I think to go and if they suffer (business) loss account of that decision then so be it. The casino/hotel may well be totally innocent but one thing is for sure they surely are no more innocent than those that found themselves in front of the automatic weapons.
Why not allow evidence or recorded video or whatever facts that are available, that might come out to allow the ultimate decision rather than people who are not in the area or have no connection to the hotel/casino or the people involved?