The only possible suit I could see is if the theater disallowed C&C permit holders to carry in the building and then I would think you would need to be permit holder and in the building at the time of the shooting to have standing.
The theater management selected the locking/door closure mechanism for their benefit (to keep people from slipping in to beat paying for tickets), and to let people get out. They totally ignored audience safety!
He sued: (1) the shooter's doctors, for prescribing him antidepressant drugs and not adequatley monitoring him (a dubious claim); (2) the theater, for not adequately guarding the exit door the shooter came in through (also pretty dubious); and (3) (I'm not kidding, but I wish I was) the movie studio for releasing an "ultra-violent movie" that attracted a psychotic shooter (an absolutely frivolous claim that should get the lawyer sanctioned).
Reading the article before posting would answer your question.
Although I don't know what angle they'd use, the one that would get the liberal/socialist/democrats panties in a big wad would be if they sued because "The theater wouldn't let us protect ourselves (no gun zone) therefore the theater should have guaranteed our safety by whatever means necessary."
When it first happened, several Freepers brought up the issue that Holmes propped open the exit door and no alarm sounded.
I don’t know if Holmes found a way to defeat the alarm, if the alarm was not working, or if the door just didn’t have an alarm period.
In any of those three instances, the theater could be found at fault.
They’re in deep doodoo.